Since most bounty activity in a bounty I manage is done OFF the forum I allow users with neg rep to join. Nothing they do is supposed to be done on the forum period. They fill out a google form for all their work. (not managing any bounties currently) I also do not allow a bounty company to run a signature campaign for tokens.

Now as far as btc paying campaigns go, this will be handled on a case by case basis. It's not hard to look at a users trust and see what they have been tagged for. So, depending on the reasoning, users with neg rep will possibly have a chance to join campaigns. (Kinda gonna be a longshot due to what happened when Hhampuz allowed QS to join a campaign and look at the DRAMA that ensued.)