The last time I renewed my driver's license, the clerk at the DMV asked if she should check me off as an organ donor. I said no. She looked at me and asked again. I said, "No. Just check the box that says, 'I am a heartless, selfish bastard.'" Becoming an organ donor seems like a win-win situation. Some 3.3 people on the transplant waiting list will have their lives extended by your gift (3.3 is the average yield of solid organs per donor). You're a hero, and at no real cost, apparently. But what are you giving up when...