I only joined bounties campaigns if I see a trusted bounty manager in charge of the project, the ratings on the ICOs link are seriously useless because many of them know how to work their way up to get high ratings.
But unfortunately, not all bounty campaigns that are managed by well known and trusted manager already means it's a good and trusted bounty. I have already experienced that one around here and i understand that it can really happen to anyone because the manager is just managing the campaign and he is not really the one who is running the ICO.