[peterwwillis]

None? When I used to work in open source for fun, you could take all the time in the world to develop the right solution. People communicated freely remotely over irc and mailing lists. Very little red tape. Easy to feel like you're actually contributing to something. You get to pick what you work on and either clean up little things or tackle big projects. All necessary information is public and easy to find by asking the group.

Really you just need fewer barriers to doing work, and to make it easier to find and publish information. A group consensus or product owner can decide if work gets merged or refactored.