I do! I have been thinking about this much like you BjoernKW.. my dream is individual bid able pivotal tasks, that are part of a coherent whole agile project. When organized the right way, the fastest person to complete them on a distributed team wins, and there would be no limit of team size.
I actually ran a request on Bountify, and it was cool. There was some pushback for programmers who thought it was too much of a project for low $, while others enjoyed completing it for the challenge (and actually got paid).
Plenty of challenges (in making this really work for companies), but I believe Bountify has a good start here.