If this big fish is dumb enough to keep playing and he is comfortable with donating his money to the poker econonmy, then I don't see anything wrong with following him around.

If you would spend your time avoiding players better than you, then there's no reason not to take note of who's worse. Remember that this game is all about trying to win someone elses money. By buying in for a game, you're unofficially signing a waiver that it is okay if you lose.