Science Friday did an interesting program on January 25, 2008 on the validity of the "six degrees of separation" idea put forth by Stanley Milgram in the 1960s. The program features skeptic Judith Kleinfeld and Steven Strogatz (author of Sync. The story was prompted by Discover magazine's story, If Osama's Only 6 Degrees Away, Why Can't We Find Him?". Kleinfeld is more interested in the human, anthropological dimension -- why do people sieze on the theory? Why do people want to believe the theory? Strogatz does an admirable job defending the math and the theory. Kleinfeld is good about reminding us that real world networks have certain constraints or laws or conventions that they obey, and when we are dealing w/ social connections that there are historical or political dimensions that we should be cognizant of.
The podcast of the program is available at http://www.sciencefriday.com/program/archives/200801256.