He See's Someones Cards

[David Sklansky]

Here is a nice question, the answer to which I haven't thought about and will not necessarily think about anytime soon. But it is a good exercise in poker thinking, so I pose it to generate some discussion.

You are an expert player and are playing in a tough game with other good players. You realize that one of the players can see a third player's cards. No one else realizes this. Does that advantage more than make up for your disadvantage? Might it depend on, the game, the number of total players, which seats they are in (assume they are sitting next to each other), or whether the player whose cards can be seen is a live one or not (assume the player who sees the cards is an expert who will make use of his information but won't make it obvious)?