To see the power of Facebook's internal API's that allow direct querying of user information, check this
graphic.
If I remember correctly, this graphic was generated by a single individual who used the documented APIs to query Facebook's database. It generated some discussion at the time because a lot of people thought it was an abuse of privacy, including the lords at Facebook who asked him to destroy his project and data.
Also yesterday, NPR's Science Friday joined the fray in nipping at Facebook's jugular. Science Friday has been an early adopter of every online community- at least, second life, facebook, and twitter. I really like the program and the podcast, but all of that "joining" has never been for me.
...Get a free T-shirt for your avatar in Second Life on Science Friday Island. I'm Ira Flatow in New York.
Note: The above includes some textual revisions from the original.