The NSA is planning to harvest the extensive information available on social networks (via Waxy).
The NSA has demonstrated a desire to build and mine a database of personal connections, so this should come as no surprise - even if it isn't particularly effective. Bruce Schneier also pointed to a great article about the problems of data mining.
Looked at this way, President Bush is only a few steps away from Osama bin Laden (in the 1970's he ran a company partly financed by the American representative for one of the Qaeda leader's brothers). And terrorist hermits like the Unabomber are connected to only a very few people. So much for finding the guilty by association.
A second problem with the spy agency's apparent methodology lies in the way terrorist groups operate and what scientists call the "strength of weak ties." As the military scientist Robert Spulak has described it to me, you might not see your college roommate for 10 years, but if he were to call you up and ask to stay in your apartment, you'd let him. This is the principle under which sleeper cells operate: there is no communication for years. Thus for the most dangerous threats, the links between nodes that the agency is looking for simply might not exist.
As Jason Calacanis put it recently, we are "living transparently" now and willfully contributing this information to public websites. Unlike the foolish high school student boasting on MySpace, a sophisticated sleeper cell is much less likely to carelessly incriminate itself on these networks. I mean, really, does the NSA expect to find the members of the sleeper cell all connected on LinkedIn or something?
The fact that we've volunteered this information does highlight, perhaps, why we are not collectively more upset about the previous NSA programs. It is important, however, to remember that there is a big difference between the government mining data to which we have an expectation of privacy and mining data that is publicly available. This is the latter case, and we have no one to blame but ourselves - but it doesn't excuse the former.
But if this data mining isn't useful to prevent terror attacks, why are they doing it? Terrorism is once again being used as a smoke screen to justify things we might otherwise be upset about.