From Bloomberg via Economic Policy Journal:
It is tiny and not growing..
Bloomberg explains:
Despite all the hype, the Bitcoin community is probably not large. It is
hard to tell how many people actually use Bitcoins. Attempts at
producing an estimate are decidedly unscientific, because people use
multiple addresses for transactions. According to Blockchain.info, more
than 140,000 addresses are now in use to process an average of 60,000
transactions per day, roughly the same number as a year ago and about
0.1 percent the number handled by MasterCard....MORE
They sure are a noisy bunch.