Cory Doctorow writes about How Your Creepy Ex-Co-Workers Will Kill Facebook . To quote:
"...Having watched the rise and fall of SixDegrees, Friendster, and the many other proto-hominids that make up the evolutionary chain leading to Facebook, MySpace, et al, I'm inclined to think that these systems are subject to a Brook's-law parallel: "Adding more users to a social network increases the probability that it will put you in an awkward social circumstance."... You'd think that Facebook would be the perfect tool for handling all this. It's not. For every long-lost chum who reaches out to me on Facebook, there's a guy who beat me up on a weekly basis through the whole seventh grade but now wants to be my buddy; or the crazy person who was fun in college but is now kind of sad; or the creepy ex-co-worker who I'd cross the street to avoid but who now wants to know, "Am I your friend?" yes or no, this instant, please... "
(Link to original article via http://www.marginalrevolution.com/)
I have to admit he has a point. Although it must be said, Facebook scores over Orkut in that it allows only 'friends' to view your profiles etc. The latter allowed just about anyone to scrap you (or at least it used to), which meant that almost any single woman claiming to live in India would get scrapped by strange engineers from Dindigul (or for that matter frustrated engineers from anywhere; let me not be parochial) about how she was sweet and asking if she would like to 'make friendship' with him.
As a counter-point, here's a paper on "The Benefits of Facebook "Friends:" Social Capital and College Students' Use of Online Social Network Sites", where they found that
"...Regression analyses conducted on results from a survey of undergraduate students (N=286) suggest a strong association between use of Facebook and the three types of social capital, with the strongest relationship being to bridging social capital. In addition, Facebook usage was found to interact with measures of psychological well-being, suggesting that it might provide greater benefits for users experiencing low self-esteem and low life satisfaction."
Then again, the "users experiencing low self-esteem and low life satisfaction" could just be your creepy ex-co-workers, or engineers from Dindigul.