Full Tilt, along w/ PokerStars, has long been regarded as a premier destination for online poker. A lot of marketing presence, a lot of players, a large range of games.
They rolled out an innovative way to play cash-game poker where you never had to wait for a hand. Several thousand people would join a, say, $1/2 game of NL Holdem, and as soon as 9 people were ready to play, they sat and formed a table and were dealt a hand. You fold? As soon as 8 other people fold, bam, you're in another hand. In practice, you never had to wait more than 1 second.
They certainly did make millions in profit on a "rake." However they have an aggressive and lucrative affiliate program that would see them paying out as much as 1/3 of a players lifetime rake to the entity that referred them to the site. (aka "Rake Back")
As an American player, until the crackdown earlier this year, I had no problems playing. When I cashed out, they mailed me a check drawn on a US bank. If I had to deposit more, I could do so from my credit card.
This is a big blow for the credibility of the industry IMO.