I'll brain-dump my second half-baked idea of the day:
github has a nice API for basically everything it does (issues getting closed,etc).
I've been working on an API for ClearCoin (creating escrow accounts, etc).
Marrying the two might work nicely. Coders could publish their bitcoin addresses in their github profiles.
Bounties could be established for bugs (or, grumble, features) by creating a ClearCoin account, linking it to the issue (maybe by posting a machine-readable comment via the github api).
And when the issue was closed via a commit the bounty could be automagically paid to the coder(s) who contributed to the commit. (somehow... via a yet-to-be-written way for ClearCoin to get a where-to-release-coins address that is not set in advance).
Reasons not to do it: allegations of corruption/favoritism if people doing the pulling have to decide between two pull requests. Maybe less cooperation to find/fix things if people are competing for bounties.