In my humble opinion, I think most these comments miss the root problem which is getting paid for the work. I know I am not supposed to plug own companies, but since we have been dealing with this very issue at the platform and process level, I will chime in with what we know. We decided that the way to go was pre-payment - ie work only begins when funds are in hand. The next questions is how to break down the chunk of work to make it easy for a project owner to pay and yet meaningful enough to the developer. We settled on a week's worth of time. Ie a developer in GroupTalent can submit a "sprint" of a week's duration working as many hours a developer would like to work in that week (most settle around 20-30hrs).

I am personally exploring a new twist in this process with the ability to force customer requirements into user stories and let developers charge for implementing a number of these stories in the same prepayment model.

hope this helps