In work with Merrie Morris and Jaime Teevan, I studied how people ask questions on social network sites through their status updates. PDFs of our three papers can be found here:

• What do people ask their social networks, and why?: a survey study of status message q&a behavior
• A comparison of information seeking using search engines and social networks
• Factors Affecting Response Quantity, Quality, and Speed for Questions Asked via Social Network Status Messages

I followed this up with Tie Strength in Question and Answer on Social Network Sites at CSCW.