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There's a problem with this, though. I'm not paying anything in PayPal bucks. I'm paying with USD. I don't need to use PayPal to pay for anything - but it's a convenient method of transferring funds from one account to another. For nearly any transaction that I could use PayPal for, I could use any number of ways to transfer funds - cash, check, money order, credit card.
I don't have to buy Paypal bucks in order to make payments through them, nor do I have to worry and fret about the exchange rate of PayPal bucks to USD. Not to mention, the buyer doesn't pay any fees to PayPal in order to use the service - the buyer does. Finally, PayPal is not subject to wild price fluctuations, since they do not use their own imaginary PayPal bucks currency. Now, if PayPal DID in fact have their own special currency that you had to buy, then that would be worth discussing.
The PizzaForCoins site updates their prices daily, which means that on any given day you could potentially be paying either a very high price for your pizza, or a very low price for your pizza. The problem is that the price of Bitcoin fluctuates on a minute-to-minute basis, and, as already established, it takes time to process and confirm Bitcoin transactions. In that time the exchange rate could be quite different.
I could just as easily pay CHEAP TOOLS directly with my credit card or send them a check. It could take longer for them to process the transaction, but I don't have to worry about the price changing between the time that I order the SOCKET WRENCH and the time that they process my payment. Heck, I can do the same with international orders. I buy from the UK every now and again. Sure, I pay a cross-border fee on my debit card, but that's for the convenience of having my bank do the exchange between USD and GBP. Given the stability of the exchange rate, I can be comfortable in knowing that I'm going to be paying ~1.63 USD for every 1 GBP, within a few cents. Just tonight, I've seen BTC go from ~1100 to 999 within the span of a few hours.
Heck, I could probably pay for my UK goods through international check, money order, or even cash if I were foolish enough to mail that. Given that the exchange rate is extremely stable over a long period of time (the average over a 5-year period is only $0.06 lower than the current rate - 1:1.57 instead of 1:1.63), I can count on the price of my Forge World models to remain about the same, inflation notwithstanding.

