I'm watching the Davis Cup final right now between the U.S.A. and Russia and they're giving both players UNLIMITED hawk-eye replay challenges. What's up with that? Have they always done this for the Davis Cup since hawk-eye was introduced to DC? What's to keep the players from challenging anything that's even remotely close? After all, there's nothing to lose since hawk-eye sometimes is a little off and can call an out ball in or vise versa, right?