[raulus]

Is it really collusion though?

For example, if I know that my buddy absolutely has to have something to complete his collection. It's an obscure item, and there aren't many other bidders. For the sake of argument, it's something that I am mildly interested in acquiring, but not really willing to spend very much. I know that my buddy is going to be willing to go nuts to get it, far more than I ever will.

Would it really rise to collusion if I decide to sit that item out?

Let's assume for a moment that all of this goes on without us actually discussing this item specifically, simply because I know my buddy and his collection, and because we're such good friends that I'm not going to be that guy.