Say you stake one of your friends into a big Pokerstars tournament, and he wins big.  He sends your agreed-upon half, and you're now a lot richer, right?  WRONG!  Pokerstars won't let you cash out the money, even if you can clearly prove that you were the one who provided the cash for the buyin (and rake) in the first place!  Think this is ridiculous?  Discuss it in our forums.