my suggest is only join campaigns that are managed by trusted managers here. Look for these managers and join their campaigns. Look for manager yahoo here and join any altcoin bounty he is managing.
Recently he is managing very few campaigns and we have to find out with the other managers who are managing the campaigns. I see good bounty should be always managed by good people only, in some cases company itself will manage the bounties but we don't know whether they are a good bounty or not.