NSA data-mining legal?

There has been some discussion on whether the recent NSA data-gathering and creation of huge databases were legal. Many in the blogosphere argue that these programs make us safer and that some invasion into privacy could be acceptable comparable to carrying around a passport when travelling foreign countries. With respect to the legality of the data collection, however, there is still an ongoing discussion in the blogosphere (in particular the blawgshere). See for example posts at the ACSblog or at The Volokh Conspiracy.

However, not much can be found on the legality of the actual intelligence process of data-mining. I also suspect that many people who write about this do not really know what data-mining actually is. The same can probably be said for another techniques that has been mentioned in this context: social network analysis.

Admittedly, both terms are not very well defined even in the research community and perhaps are best defined as umbrella terms for extracting information of vast ammount of data via statistical or machine learning techniques or via algorithms developed in graph theory.

Even though we don't no much about the programs NSA runs on these data, we need to assume that they hope to find certain patterns and eventually individuals that may be terrorists. It has already been mentioned that these methods don't avoid so-called false positives. In other words, everbody in this database could potentially end up as a terrorist suspect.

I would assume that being a suspect goes probably beyond what Americans seem to accept as giving up some of their privacy. In addition, it seems to be only a logical next step for the NSA analysts to develop dedicated databases that contain individuals that are in some way suspicious, such as critical journalists.

Currently, another wiretapping scandal is being made public in Germany where the national secret service (BND) wiretapped journalists who in particular reported on the German secret services. The journalist Peter Schütz had a wiretapping device in his appartment, according to the weekly magazine "Stern".

Moreover, not only the German secret service was involved, but there are also connections to the NSA. The NSA supposedly keeps a database with the names of critical journalists called FIRST FRUIT. (source: Tagesschau)

So, how is that supposed to make us safer?