Recently when I have seen Stack Overflow results in Google, I have seen something like this:
Note the text, "9 answers". Does Stack Overflow do anything special to get this shown? I have noticed a similar Rich Snippet on Yahoo Answers, which also said "Solved".
I skimmed the source of both pages and couldn't see anything specific that looked like a microformat. There is nothing on schema.org specifically about Q&A. Is Google treating these sites specially?