Originally Posted by PornMD

UltimateBet.net, AbsolutePoker.net, PokerStars.net, PartyPoker.net, FullTiltPoker.net etc. all have pay sites on the .com. Their bet is that a percentage of the free players will eventually convert, and they have the free sites to indirectly legally push their gambling sites on TV commercials et al (i.e. advertise the non-gambling free .net site on TV in efforts to convert some of them to gambling pay .com site players).

The other model of poker site is the monthly membership "sweepstakes" sites like SpadeClub.com and ClubWPT.com. both are $20/mo and have only freerolls etc. to win money (and ClubWPT.com has a corresponding TV show such that you can win all-expenses paid trip to Vegas + entrance on the show which is a 1-table tourney to win $5k.