A good post and a fascinating discussion over on Don Park's blog on the potential adverse effects of social software, starting from his observation of how the Internet affected people in his home country:

Korea is emerging as one of the most advanced Internet nation in the world.  Young Koreans, in particular, live and breath Internet, each belonging to large number of online communities.  One would expect them to be well informed and objective, yet they are not.  Their views are warped and often radical.  While all the world's information is at their fingertip, they consume information subjectively and produce misinformation biased by their views.  Adding highly effective social software to this is frightening to me.

[...] In a sense, social clusters form gravity wells which has its own local physical laws and is difficult to escape from.  Social softwares make it easier to create and grow such clusters.

Bill Kearney offers a counter-argument that I find cogent:

The fact that groups can form more rapidly will do more to devalue the ability of any one group or cult of personality. Yes, for those ununsed to the process it will be a terrifyingly vast expanse of rapidly changing groupings. Hang on, it's going to be a fun ride.

I guess the question could be summarized as "Does social software help people turn inwards or outwards?" - and I don't think it can be answered without taking the context of use into account.