The figures are amazing. I would love to see some Facebook research people calculate the "six degrees" using their user's networks. What would the average x be in "x degrees" for two avarage users on Facebook?
Years ago Facebook had a feature that would show you the shortest paths between you and the person you were looking at. I don't know if they got rid of it for privacy or performance reasons, but it was pretty cool.
A company called Sysomos did a similar analysis for Twitter. Unfortunately their analysis is a bit ambiguous, but it's an interesting read nonetheless. http://sysomos.com/insidetwitter/sixdegrees/