Guideline for doing a bounty right, based on bitter experience:
1. If you want something open source, demand that the person START doing so right now, and from an publically accessible codebase. Don't buy his "not ready" bullshit, even if said bullshit is true. You will be left with working code but not ownership of the codebase itself, which mean you can't fund other people to work on where that programmer left off. Don't forget the license either.
2. If the person is going to escrow some kind of funds, demand that person to state a clear date by which bitcoin get used or returned to the pledgers.
3. You should do your escrow of funds at the last possible moment. If a person disappear from the scene, you can't get the bitcoin back.
4. Never give large amount of funds to somebody who is new.
5. Never donate money to somebody who is inactive in the forum.
I violated some of these rules myself, so I will be following them as well.