A more effective idea to remove bounties from spoiling the forum would be to remove the ability to merit in bounty threads or boards.
I would really love to see Theymos experiment on removing every bounty and signature campaigns and let's even see how things will pan out here with all these hypocrites denying they aren't posting here for reward, especially the high ranking members. At least, one month should be ok to test run this and see if posting activities won't be drastically reduced and traffic affected here.