Most of the discussion has dealt with whether or not StackOverflow should be open sourced, but a more interesting question IMO is what tangible (ie. non-idealogical) benefits the community could hope for in the event StackOverflow was open sourced.
Full disclosure: I feel that open sourcing StackOverflow is a bad idea so long as StackExchange is around; should that venture be abandoned, and the StackOverflow team will to put up with the time investment, then I can't see a compelling reason not to.
Assume that some time from now StackOverflow is open sourced, with a well defined process for submitting patches (and, presumably, a few new employees to type "Decline" all day :) ).
What features, improvements, "bug" fixes, or the like would you contribute?