I answered this question with a bounty leaderboard.
To the question, should the site have an area where you can see a bounty leaderboard (monthly, yearly)? Yay, nay, waffles?
I don't think there's an obvious benefit to SO to having a bounty leaderboard. The bounty questions get plenty of exposure as it is. Sure, it's a nice bit of statistics, and some people might get a warm fuzzy feeling pretending to be Han Solo, but is the impact on SO positive, neutral, or negative?
We should have a bounty leaderboard if only to expose me as a greedy, greedy bastard. It's the only way I'll learn.