Social networking sites make it very easy to stay connected with one's friends, colleagues and acquaintances, all at the same time without having to disturb them with intrusive calls for 'updates'. Facebook 'updates' are a lot better at keeping one informed about one's social circle. However, despite it's 'private' feel, Facebook and other similar social networking sites are not exactly 'private spaces' protected by right to privacy. Information one shares with your 'Friends' on Facebook is subject to and governed by the laws.
It is certainly possible to make sharing private by the privacy setting for each post or by communicating through Facebook messages (inbox) instead of 'posts' and 'comments'. But in that case one uses Facebook not as a 'social networking site' but as a tool much like e-mail, which is just the electronic form of ordinary mail.
Since social networking sites have changed the way we connect, communicate and share, it is important for the users to understand the adverse legal consequences of being too easy with what they say and share on such sites.
The host sites, like Facebook, Orkut and Google, are not really 'guilty' for the user-generated content; the users are. Where there is legal accountability, one must be a lot more careful than the users generally are.