I used to tease my cycling buddy about getting his nuts caught in the ventilation hole in his seat while flying over his handle bars. I suppose bicycle shorts would help in preventing this sort of tragedy.
I used to wear cycling shorts more than I do now but I find they just too uncomfortable to be in off the bike. I stick to short 20 minute sprints around the at a time though. They're padded and cost about 40 bucks but I can't shake that diaper feeling down there. They're nice for longer ride though when I'm not climbing off my seat every 5 minutes.