Here's an issue that I perceive:
Google Groups and systems that mimic Usenet are technologically poor avenues for Q&A (at least relative to what Stack Exchange has evolved.)
Stack Overflow has fairly aggressive criteria for closing or downvoting "unwelcome questions". While I've found out that "too localized" has gotten the axe as a close reason, I am skeptical that a question like "Why can't I compile dungeon.red" would receive a welcoming response.
(Correct me if I'm wrong, but established convention seems to be that questions regarding problems or bugs in an incidental demo program I wrote, would be deemed as unfit here... and belonging on, say, a Google Group instead. But this gets back to point #1: why shoo people and make them use something not good... with no markdown preview, no versioning, no wiki updating, etc. etc.?)
Could certain questions that are "not good enough for Stack Overflow"--be marked with some kind of "second-class-citizen" status? Maybe they don't show up on the general site, but only to users who are subscribed to a certain tag... or go to the absolute bottom of search results? Could there be a way to let Q&A which may not be of paramount interest live here? A softer triage than "close", allowing the interested parties to have access to the questions and answers?