Before participate in bounty campaign - do some research about project (team, media activity, wp). Also check bounty manager trust. And then make your decision.
This is exactly what I'm doing before participating any bounty campaign. You will spend your time and effort so better to review all what you've mentioned. Better safe than sorry. Plus I joined the project that close to my values, something that I believe in. That is mostly my criteria. So once the business prosper, I felt extra happy about it.