[Air-L] Sampling and recruiting in Social Networking Services

[Alexander Semenov]

Hello everybody,
I'm interested in any information about sampling and recruiting people in  
SNS to participate in any kind of online surveys, panels, questionnaires  
etc. After some googling I've found only several blog postings, like this  
ones:
http://kurtisrandom.blogspot.com/2007/11/sampling-massive-online-social-networks.html
http://vannevarvision.wordpress.com/2007/10/04/review-analysis-of-topological-characteristics-of-huge-online-social-networking-services/
http://researchreinvented.blogspot.com/2007/12/recruiting-using-social-networks.html
But I wonder whether there are any "serious" articles on the question?
Thanks in advance.
Alexander Semenov.