Miners aren't compelled to include transactions in a block, and blocks containing no transactions at all are perfectly valid. However, transaction fees provide an incentive for them to do so. Currently, most miners are willing to include transactions without fees under most circumstances, as most of their income comes from the block subsidy rather than transaction fees, however it is likely that transaction fees will eventually be required for all transactions, as the block subsidy is halved every four years and will eventually become a negligible portion of mining income.

You definitely need to find a new accountant. Preferably one who actually knows the meaning of the word "investment".

Yes, and in a big way. Virtually all web wallets use them. Eg, suppose Alice, Bob, and Charlie all have an account with the same wallet provider. Alice and Bob deposit BTC5 each, and Charlie deposits BTC10. If Charlie then sends "his" BTC10 somewhere else, it might actually come from Alice and Bob's deposits. It's exactly the same as if you deposit $100 cash in your bank account, and then withdraw it again later: the bills you get almost certainly won't be the exact same bills you deposited, they'll have likely come from another depositor, or even several different depositors. The assumption that all sending addresses belong to the same owner is bogus if web wallets are involved (unless you consider the web wallet itself to be the "owner"), and so is the assumption that it's safe to send a refund back to the original sending address, since that address might not actually belong to the person who originally sent the money at all.

Food is a better carrier of energy than the body fat it produces. You can save a lot of energy by cutting out the middleman, so to speak. (Of course, in The Matrix, the reason they were harvesting humans for energy was that pollution had blocked out the sun, so they couldn't use solar power. Which raises the question of how they were able to grow food to keep the humans alive in the first place. And any means of producing food artificially would consume more energy than you would get out of it. It's physically impossible. The whole central premise of the movie falls apart completely if you actually think about it for two seconds. Very disappointing, since most other movies take at least five seconds of thought before you realise they make no fucking sense.)

Stephen Gornick, your estimates for 2009-2010 are wildly optimistic. In May 2010, a bitcoin was worth a quarter of a cent, judging by the price of laszlo's pizzas. In late 2009, it was worth about a tenth of a cent, if New Liberty Standard is to be believed. Before that it was worth nothing.

I'm sorry, but I really don't get it. I'm agreeing with you. I never said it couldn't be done. I said it couldn't be done without a vastly improved cooling system, which isn't practical in most cases. Unless you think using a 15 times larger heat sink to get a measly 0.7 watts is practical (I don't).

IANAL, but in most places (it would be helpful if you were more specific), if you earn bitcoins by mining, or as payment for services, then you have to pay regular income tax on the fiat value of your bitcoins when you received them. If you bought bitcoins at an exchange, there is no income tax, but if you later sell or trade your bitcoins for more than what you paid for them, then you have to pay capital gains tax on the difference (if you sell or trade your bitcoins for less than what you paid for them, that's a capital loss which may (or may not) be tax deductible). Bitcoin donations are probably not tax deductible in most cases.

If you search this forum, you will no doubt come across absurd arguments that bitcoins aren't taxable because they aren't real money, or aren't really property, or some other ridiculous reason. Most governments don't actually care about any of that. It doesn't matter in the slightest whether bitcoins are money, a commodity, virtual property, or something else entirely; as long it has value, and you make an income or profit from that value, then you have to pay tax on that value.

There's an even more obvious issue: cooling a chip and using it as a heat source for an engine (of any type) are mutually exclusive goals. If you have an effective cooling system, the chip won't get hot enough to provide enough energy to run it, as preventing the chip from getting hot is the whole point of having a cooling system in the first place. If it does get hot enough to produce a practical amount of energy, your cooling system is obviously not doing its job. It's most unlikely that any sort of heat engine will allow for more effective cooling than a simple heat sink; that's simply not what heat engines are designed to do. Like I said: possible, but almost certainly not practical.

Say what? Last time I checked, bitcoins were worth something. Free energy costs nothing. How does something - nothing = not profitable?

No, it's just a heat engine. Heat engines produce energy by transferring heat from a heat source to a heat sink. In the absence of an external energy source, this will eventually result in the heat source and heat sink reaching thermal equillibrium (ie, the heat source gets cooler and the heat sink gets hotter until they're both the same temperature), at which point no further heat transfer can take place and no more energy can be produced. To continue producing energy, you need to either actively heat the heat source or refrigerate the heat sink, both of which require you to put in more energy than you can get out.

Heat engines can be useful for recovering energy which would otherwise be lost as waste heat, but can never produce more energy than you were wasting as heat in the first place (and in practice, they don't even come close to that).

I never said it wasn't possible. I said it was less effective and more expensive than conventional cooling, and that the chip absolutely has to be cooled by something other than the heat sink. It's not impossible, just very impractical.

Actually, they are practical for some applications. Just not applications where you absolutely, positively, need to get rid of waste heat.

No it doesn't. As I previously mentioned, the heat source and the heat sink must be thermally insulated from each other in order for a thermoelectric generator to work. And if they are thermally insulated and you have no other cooling system, the chip burns to a crisp. There is no potential here.

You do realise that thermoelectric generators insulate the heat source from the heat sink, right? Otherwise the heat just gets conducted straight to the heat sink without producing usable energy. Needless to say, this is precisely what you don't want on your mining hardware, as it will result in greatly increased temperatures, which (since the chip has a constant volume) increases the pressure of the magic smoke. This rising pressure is very likely to rupture the chip's casing, releasing the magic smoke and rendering the chip useless. While you could use the output of the thermoelectric generator to power an additional cooling system, a conventional heat sink provides far more effective cooling at a fraction of the cost.

Seriously? The purpose of this is that buying things online is more convenient than having to go all the way to a store. Naturally, you can't pay cash when shopping online, so some sort of electronic payment system is required. And Bitcoin is faster and has lower fees than any other electronic payment system on the planet. That's the incentive. You're not anonymous when purchasing these goods as your name and address is needed to deliver them.

Ah, yes, the old "If you've done nothing wrong, you've got nothing to hide." Well, let me tell you something. I've done something very wrong. I got a girlfriend. What's wrong with that, you say? Well, I don't know either, but her jealous and abusive ex seems to think I've done something wrong, and he says if he ever finds us, he's going to kill us both. So you'll have to forgive me for "not having the balls" to ID myself.

Nah, I'm just kidding. My girlfriend doesn't really have a jealous and abusive ex. You see, the real reason I won't ID myself is that I once did a... "modelling job" to help pay for college. A search for my name reveals some, ahem, pictures that I'm not entirely proud of. Dammit, had I known those pictures would be used as the "before" pictures in advertisements for a certain penis enlargement product, I never would have agreed to it. Anyway, I'm hiding my penis (please, no jokes about having "nothing to hide" ).

He's a Windows user, silly. In case you don't know, Windows absolutely requires a GPU to enable most GUI features (rendering in software is not even an option, even if your CPU could handle it), which has forced people to buy expensive graphics cards for the sole purpose of running the Windows GUI, even if they don't intend to ever do anything else with it. Hence the term "GUI card".

Yes. He had a car.

Settle down, the current state of fusion research is nowhere near as advanced as you hope.

Yes, fusion reactors exist, and you can even build one for only a few thousand dollars if you know what you're doing. But there are a couple of problems. First of all, most fusion reactions (including all of the most practical ones) produce a huge amount of neutron radiation, which (unlike most other forms of radiation) causes anything exposed to it to become radioactive. When the reactor components wear out and need replacing, they will be highly radioactive and need to be disposed of as such. Anyone claiming that fusion reactors produce no radioactive waste is lying.

The second problem is even more serious. To get nuclear fusion, you need to produce and confine an extremely high temperature plasma, and no current designs* have been able to achieve this without consuming more energy than the fusion reaction produces. (Note that a loss of plasma confinement is not particularly dangerous, as although the plasma is at a very high temperature and pressure, the density is so low that it's virtually a vacuum, with a correspondingly low heat content. Instead of the reactor heating up and melting, the plasma cools. Cool plasma is no good for fusion though, so confinement is still extremely important, but losing confinement isn't the catastrophe that one might imagine it to be.) No currently operating fusion reactors are capable of producing net power, and all are used either for research purposes or as a controllable source of neutron radiation.

*Nitpickers will be quick to point out that fission bombs are capable of producing high temperature plasma and confining it just long enough to get a good fusion reaction out of it without consuming much energy, but this has an obvious drawback.

Mined coins are normally sent directly to a public key, rather than an address. An address is a specifically formatted hash of a public key to make it easier to manage (specifically, an address is shorter than a public key and a typo will (almost) always result in an error message rather than sending the coins to nowhere). Addresses are not needed for mined coins (technically, they're not even needed for regular transactions, as you can send to a public key directly (in theory, anyway - in practice, most clients even won't let try you do this, due to the fact that a typo will mean the coins are gone forever)). You will be able to spend your mined coins (and any other coins sent directly to one of your public keys instead of one of your addresses) as normal.

How? The blockchain isn't an ecosystem, it's essentially a special-purpose cloud-storage service. Storing information (normally financial transactions, though any kind of information can be stored in the blockchain if you want) in exchange for a fee is the whole purpose of the blockchain. That's what it's designed for and that's what it does. Storing excessive amount of data in the blockchain isn't "pollution", it's ordinary use of a service in the way it is purposefully designed to be used.

Nobody other than miners even needs the full blockchain, and miners charge a fee to add to the blockchain to cover their expenses. A pruned blockchain is good enough for non-miners, though of course they're free to use a full blockchain at their own expense if they want. And that expense is very minimal. Hard drives are cheap and getting cheaper all the time.

You're using the wrong tool for the job. Sarcasm detectors don't function as expected when your interlocutor truly believes what they say. For these people, you need a BS meter. When dealing with people like cunicula, be sure to set it to high-range mode to avoid overloads.