It works for the very small set of people who have bitcoins they haven't bought with a traditional currency. This is bigger than the set of miners, but not by much.
> This is bigger than the set of miners, but not by much.
From bitcoincharts.com quickly estimating that the volume in exchanges was 2 million BTC. Bitcoins produced by mining = 3600*30 = 108000 BTC. Unless the speculators are constantly buying from each other, I would say that there are people earning bitcoins in the bitcoin economy, and the amount of those people vastly outnumbers the miners.
But I doubt that they care that much about the pizza service...
You would wager wrong, depending on how you define "large." The total exchange volume of all exchanges is only about 93k BTC per day. http://bitcoinwatch.com/
The daily transaction volume, with change transactions removed, averages around 400k BTC per day.
So speculator trade is less than 1/4 of all Bitcoin transactions.
Fun fact: SilkRoad is less than 3% of daily Bitcoin transaction volume
75% of trades are commercial in nature. There are thousands of vendors dealing in BTC- hundreds of which deal in it exclusively. Some are even among the most popular web sites in the world.
25% of the daily volume (100K out of 400K) is pretty huge if you ask me, yes.
How much is money-laundering? How much is people just moving stuff around for the hell of it? Of what's left how much is online gambling (an economic activity but not necessarily a 'good' one)?
These things would be very hard to tell I would have thought.
