In an age of social media and networking, it is quite likely that your prospective employers want to know more about the 'Real' you, while they are considering you for a position. While it is understandable that they need to get a responsible person for the position, it is quite unreasonable that they go over your profiles and posts in Twitter, Facebook, Blogger, Myspace, Orkut and the like. Going over it in Linkedin, the professional site is understandable, but not the others.
These sites are more a platform to voice out your opinions on current topics and one definitely has freedom of expression and thought. Maybe using unparliamentary language, commenting abusively or posting pictures that ought to be private, is not a ethical thing, but having your own opinion on things is not wrong. Its your personal space and you have the authority to say things out.
If one is going to judge you based on your posts rather than your technical skills and people skills, it is indeed unfortunate. I would not call this kind of networking as a part of social skills (even though it actually is), since it is something that is private and a good line has to be drawn between professional and personal life.
(Thanks to Prathap for initiating this discussion and also to Harish for bearing with me in the discussion :).)