"The psychologist Dr Aric Sigman says that social networking sites undermine social skills and the ability to read body language. Actual physical contact benefits our wellbeing by boosting levels of the hormone oxytocin. In fact, being lonely is as bad for your health as smoking."

Aric Sigman has a previously spoken on the matter and has had most of his points debunked already, see Ben Goldacre's post here:

http://www.badscience.net/2009/02/the-evidence-aric-sigman-i...