Why does anybody "follow" anybody else's plays.
Once in a while I don't have time to cap a game I am interested in, I might tail, but that is by no means done on a regular basis. Maybe somebody nudges me off the fence on a game I like.
The most I may do is adjust my wager size a little either with or against somebody.
So to answer your question, nobody has cost me any money. (Thats just me though)