I've pondeded Tank's theory and I think I'ts pants! (I can say that, he's my mate)
It dosen't matter if a fish wins money from a fish or a good player wins money from a fish, both players are going to continue to play and pay the rake
It is just that, a theory. I'm going to swing about with it a bit more before I chuck it on the fire though.
I understand that a lot of fish will continue to play indefinately, funding their poker account with money from their recreational budget. Surely there must the type of player who after they lose a certain amount of money, give poker up as they can't afford it.
A fish will continue to play, on the most part, because they will win sometimes. The more sharks at the site, the less likely a fish will have a winning session. They might start playing at one of the poker sites competitors if they always lose or even quit the game altogether.
I've played on a fair few websites, used them for a while and moved on. I cashed out of all but one a winner. The one where I lost my initial deposit sent me all manner of offers and incentives via e-mail and post to come and play again. All the others sent me close to nothing once I moved away. This would suggest poker sites do care what type of player you are when it comes to courting your buisness.