Bitcoin has been around forever, but it's been relegated primarily to the geek underground subculture. It's quite popular with the underground type sites -- which I guess online poker in the US has been forced to become -- that want to accept funds or donations from users, since the conventional "legit" avenues like PayPal
and such often forbid transactions for anything they deem unseemly (porn, piracy, gambling, etc.). For instance PayPal has recently been cracking down on a lot of web sites that cater to downloaders (usenet, bittorrent) who were funding their operations through PayPal donations. A lot of those types of sites are moving to bitcoin. I've also seen a couple of poker sites
start up recently around bitcoin.
The problem I see is that bitcoin is still mysterious and inconvenient for most people, and there's the security aspect of it. Just about anyone can become an exchange -- unlike other financial institutions or even online wallets like PayPal (which has become a regulated financial institution of its own), there's little to no oversight or regulation. Sure, the top exchanges are safe and have large user bases who can attest to their credibility, but it's still off-putting to a lot of people. Plus the exchange rate fluctuates daily, something new to most US people (the non-US folks are having a laugh at this notion, I'm sure). Last I looked the rate was around $13US per bitcoin. Also, a lot (most?) exchanges don't accept credit cards or EFT's, only wires or other inconvenient transfer methods.
Poker players though may be just the type of risk-takers who are the ideal market to kick up bitcoin popularity. I guess time will tell.