I think Jeff was always very keen not to make it a social network and focus on pure Q&A. Ie there is no ability to follow people/friend them etc which you can do on Quora for example.

http://forrst.com is another.

And also http://geekli.st/ - even though it's not technically programming oriented, all of the top communities on there are programming related.

I've always viewed Forrst more designer than programmer

It seems to have turned out that way but officially it's always been "developers and designers" with a slant towards front-end work.

I was interested in http://geekli.st/ until the OAuth login required me to allow "Update your public repositories (Commits, Issues, etc).". What's up with that?

And here, I always thought of GitHub like that...

Also Geeklist, as of late.