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

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-netw... http://vannevarvision.wordpress.com/2007/10/04/review-analysis-of-topologica... http://researchreinvented.blogspot.com/2007/12/recruiting-using-social-netwo... But I wonder whether there are any "serious" articles on the question? Thanks in advance. Alexander Semenov.