As the "Roy Halladay sweepstakes" drag on, the question about whether to deal four or five top prospects for one player keeps coming up. The Phillies in particular seem to be playing hokey-pokey with J.A. Happ. Is it a good idea to trade top notch prospects for a potential Hall of Famer? Well, I decided to look at history to see what it can tell us.Obviously, it is rare that a former Cy Young winner gets dealt, but it has happened often enough to give us a track record: (note that I...