It's quite simple. Size is the number of euros that people are offering to buy/sell, price is the number of ripples they want per euro, and sum is the cumulative total sizes of the orders, ie, the total number of euros that must be bought/sold to reach that price.

To give an example of how it works, say you want to trade 10 euros for ripples at market. How many ripples would you get? Well, you'd get the best bid price for your euros, which in this case is 81.37 XRP per euro. But you can only sell 5 euros at that price, so for the remaining 5 euros, you get the next best bid, which is 80.98 XRP per euro. But again, you can only sell 4.35 euros (9.35 total) at that price, so you sell the remaining 0.65 euros for the next best bid after that (75 XRP per euro). This bid is finally large enough to sell all your remaining euros, so we're all done, and you've sold 5 euros for 81.37 XRP each (406.85 XRP), 4.35 euros for 80.95 XRP each (352.1325 XRP), and 0.65 euros for 75 XRP each (48.75 XRP), for a grand total of 406.85 + 352.1325 + 48.75 = 807.7325 XRP. Average price = 80.77325 XRP per euro (or 0.01238 euros per XRP if you prefer).

Buying euros with ripples follows the exact same sequence, only you use asks instead of bids (and so you'll pay at least 205 XRP per euro due to the massive bid/ask spread resulting from the ridiculous illiquidity).

You just answered your own question. Because the private key is known, the instant anyone sends coins to that address, somebody will attempt to transfer those coins to their own addresses before anyone else does. But since everybody else has the exact same plan, the result is a great many transactions from many different people all trying to spend the same coins.

No. Goods and services are not debt. When you grab goods off a store shelf, you don't owe the store anything (unless you walk out with the goods without having bought them, but that has its own problems). Ever wondered how stores are allowed to refuse to accept $100 bills, even though $100 bills are legal tender? It's precisely because they're not required to accept legal tender. Now, if you steal something from the store, get arrested, and the court orders you to pay for the goods you stole, then you have a debt and the store is forced to accept legal tender, but otherwise they don't.

No, because that painting isn't payment for services rendered, which is what mined bitcoins are. They are the payment that miners receive for securing the Bitcoin network. If you receive anything as a payment for services or any other kind of work you did, that's income and you have to declare it.

There are two types of taxes you need to worry about with Bitcoin.

The first is regular income tax. If you earn bitcoins by mining or doing any other kind of work, you must declare the market value of your bitcoins as earned income whether you sell them or not. In some jurisdictions (I'm not sure about Greece), this also applies to gifts and gambling winnings. You do not have to pay income tax if you simply bought your coins on an exchange (but see below). You may also be able to claim a deduction on any expenses relating to your bitcoin earnings.

The second is capital gains tax. If you sell or otherwise trade your bitcoins (regardless of how you acquired them), you have to declare the difference between the market value when you acquired your bitcoins and the market value when you disposed of your bitcoins (eg, if you bought BTC100 for €2000 and then sold BTC2 for €200, you would have to declare a capital gain of €160, since you bought your coins for €20 each and sold for €100 each, so you made €80 profit per coin). If the market value when you disposed of your coins is lower than when you acquired your coins, you have a capital loss which you may (again, I don't know what the law is in Greece) be able to claim a deduction on.

I'd advise you to consult an accountant (instead of random people on the Internet) for further clarification of your tax situation (especially regarding capital gains tax, which can get quite complicated). As you point out, if you deposit large sums of money to your bank account, the authorities will find out about it, so be sure to declare it correctly on your tax return.

It's because altcoins are typically traded for bitcoins, not fiat. There was never a drop in value of altcoins, ie, they were still worth the same number of bitcoins. So when the fiat value of bitcoins drops, so does the fiat value of all altcoins. Note that the more volatile an altcoin is, the less noticeable this effect is as it gets lost in the "noise".

ASIC does, however, regulate "custodial or depository services". If you're holding AUD deposits on behalf of your clients for withdrawal at a later date, you need an AFS licence.

If you "believe in taking advantage of regulatory compliance", how come I can't seem to find you in the AFS Licensee Register?

The only way you could possibly know that for a fact is if it was your referral link. So much for the "hacked account" story.

You don't trust escrow as well, you trust them instead of the person on the other side of the trade. Big difference. Ultimately, you always have to trust someone (except, perhaps, for purely digital contracts, though that's still a ways off); escrow just gives you a choice of who to trust (presumably, people trust escrow more or they wouldn't pay extra for it). Of course, escrow is not necessary when dealing with reputable merchants, or at leasts ones that can be held legally accountable if things go wrong.

That was just an apartment building, as everybody who bothered to actually check the address would know.

Might I strongly recommend that the first thing you connect to your generator be an AC voltmeter?

It does because i² is -1, and amazingly it works the other way around too, so 2ⁱ is also -1. e is just 2 with some extra digits which we can ignore since we're dealing with integers here, so eⁱ is -1 as well. And of course, π is an odd number, so -1 raised to the power of π is still -1. Ergo, e^iπ = -1. Q.E.D.

Of course. If you plan on visiting Australia, leave your porn of small-breasted women at home (yes, Customs does actually check for that).

What's this "tried" bullshit? When we Australians attempt a thing, we bloody well succeed at it! I am not proud.

That's not stopping them at all, since they can set prices in fiat and sell their bitcoins as soon as they receive them. Payment processors such as BitPay can do this automatically for a small fee. Volatility is a total non-issue for merchants.

Yes, since the only way for bitcoin to reach such a price is a massive increase in demand, which means more capitalization and liquidity, with the result that it takes more money to produce price swings of the same magnitude.

It would be exactly the same. A 5% drop is a 5% drop no matter what the price is in absolute terms.

The reverse would be the case, for the reasons previously mentioned. Higher price = less volatility.

It's a scam.

Buy and sell are, respectively, the lowest offer (what you would have to pay to buy) and the highest bid (what you would get if you sell). Does not mean that a trade has actually taken place at this price.
High and low are the highest and lowest trades in the last 24 hours.
Last is the price of the most recent trade.
Average is the average price over the last 24 hours (volume divided by vol_cur).
Volume is the number of bitcoins traded in the last 24 hours.
Vol_cur is the number of currency units (litecoins in this case) traded for those bitcoins.

No it isn't. You can't judge the value of a person's life based on what they might do in the future. By that logic, you might as well say "What if your grandchild was to become the next Hitler?"

You want me to sell all my coins? Down to my last satoshi? Okay, my price is 5 million times Earth's gross planetary product. (Some people here say they'd never sell their last satoshi, not for all the money in the universe, but I'm slightly more flexible on this matter.)