Dr Sigman was interviewed by the BBC and you can hear the report, and read more about his article here.
In brief, Dr Sigman warns that the aim of social networks - to keep people in touch - could be having a negative effect, especially on younger users, for whom online interaction increasingly is replacing face-to-face conversation.
Naturally, there are pros and cons to this argument, with respondents to the BBC article arguing for both benefits and harm caused by the use of social networking sites.
Film stars repeat YouTube success story - News - South Manchester Reporter
As a brilliant counterpoint to Dr Sigman's assertion that too many young people are online too much, up pops a fantastic short film, made by two 20 year old Media students at Manchester Metropolitan University.
How To Say I Love You cost £200 to make, was shot in a morning, and garnered 650,000 hits in its first 24 hours on You Tube. Since its first posting a month ago it's had more than 1.7 million hits! Its makers, Hayley Stuart and Francesca Sophia, have produced a sharply observed commentary on how the Facebook generation still wants old fashioned romance to sweep them off their feet. It's just that for teens brought up on rapid Status updates, there isn't always time to waste on small talk.
How To Say I Love You is a powerful short film, that warrants your attention. Stuart and Sophia's previous YouTube upload, Olivia - Explorer, made for £7, has received over 1.3 million hits. Expect to see more from these two in years to come. Exceptional talent.