when the question is asked or do the users decide if they would like to see it on the social networks and select it themselves?
Edit - This is on the main site, the Q & A side.
Basically it's up to each user to decide whether a question should be posted onto one of the social networking sites.
There are the sharing buttons to the left of each question which lets any registered user post the question to Google+, Facebook and Twitter.
If you post an answer there is also sometimes a text reminder - depending on the views/votes of the question.
You can also copy the "link" URL and post that on any other social/business network of your choice (reddit, LinkedIn, MySpace...).
There is a also a Twitter account for each site that posts questions (I'm not sure how that works exactly) and Google+ feed as well.