I believe this would be in the context of the snack machine and fast payment processor.  Since there is only a few (~15) second window for double-spend you don't dispense the sugary snack until that amount of time has passed.  If you do detect a double spend you block the coin and don't dispense the healthy/sugary snack, no one but the malicious owner is affected.

I'm sure a payment processor could block the coin within it's own network, but it could still get in someone else's block later.  If everyone blocked it then in the case you're speaking of, outside of the snack machine context, both recipients would get screwed.

Good point, what if it's just the first 4 characters of the SHA-256?

If your labor is worth $3 an hour but the minimum wage is $6 an hour, you don't get the $6 an hour at a $3 an hour loss to the employer. You get nothing because you won't be hired. You're presenting a false dilemma. The choice isn't between $3 an hour and $6 an hour. The choice is between $3 an hour and nothing. Whatever can be said about getting $3 an hour, a lot more can be said about getting nothing.

Is like the police setting up a speed camera and you getting a fine in the mail two weeks later. It does nothing about the speeding at the time you did it.

It would be helpful if you could know why someone voted you up or down. The current system is innefective in changing behaviour because you dont know wtf you did to deserve ratings.

If 10 trolls give you a negative rating wtf does that even mean ?

Id like to see who gave a rating and who rated other people. That is more important than seeing a pointless number count going up or down.

Take the bitcoin-otc for instance.....

If prices were set in gold, then the price of gold wouldn't vary drastically. The only reason the price of gold and bitcoins vary drastically is because they are being compared to the dollar and a) the demand for dollars vs. bitcoins or gold varies over time and b) central banks arbitrarily alter the supply of fiat money.

If you look to history, you will see that prices and wages were once set in gold, but have not been since the establishment of legal tender laws. Particularly, look at the attempted introduction of state backed notes on the west coast, and how they fared compared to gold/silver until federal legal tender laws were enacted.

So, what you all think?

People who use GPG: How do you back up your private key?

I'm using a passphrase-protected private key with what I consider to be a strong passphrase (quite long, no English words, no personal relevance, etc). Do I need to be protective of this key? My guess is that it's symmetrically encrypted using some derivative of my passphrase, so it should be unusable by anyone without my passphrase. If that's the case, I could post it on a billboard in Times Square and no one could do anything with it. But I keep hearing that I need to keep my secret key secret, so it's possible I'm missing something here. What is it?

By that line of reasoning, why say 100 Bitcents when you can say 100000000 Satoshis instead?

Bad idea. What happens when two people use the same password?

In a one-shot game, there is never any purely financial incentive to reject whatever offer.  As I said, not even a 5000$/0$ one.

Keep in mind that a node will not forward a transaction if it has already seen one that conflicts.  

... the _only_ person who can double spend is the owner of the coin (since only he knows the private key). The only time clients see a double spend is if the owner is purposely being malicious. It is therefore reasonable to drop _both_ the original and the second transactions if a double spend is seen within a window of time. Further, the double spend "event" could be bundled (both original transactions included in the bundle as proof of the double spend) into a transaction that locks that coin out for a long time (remember, we have proof of malicious intent so we would be justified in locking out the coin for say 10,000 blocks or more).

After the [15 second] window of time expires the second transaction is simply ignored. At this point we don't want to lock out the coin because we don't want to leave an opening for the original owner to cancel the original transaction. We would need the window to be large enough that we are very confident most clients have seen it yet short enough that the selling merchant can wait without burdening normal customers. 15 seconds for example. So, waiting 30 seconds without seeing the coin lockout transaction would assure the merchant no double spending happened.

NO, unconfirmed transactions with no special attempts to ensure finding double-spend transactions are not acceptable for any automated system.  In the standard client, even if your client does hear about a double spend, it doesn't mark the double-spent transaction of notify you in any way.  If an attacker created to transactions, sending one to the largest miners (not hard to figure out their IPs) and one to you (depending on the way you structure it, also probably not hard to find your IP) and you would be none the wiser.  Even if you purposefully modify your client to mark double-spent transactions, you have to make sure you have a direct connection between you and the miners attacked to ensure the nodes in between don't drop the double-spend you want to know about.