And in fact, a few people have mentioned that the intelligence agencies had a bit of forewarning about Major Hasan (at Ft. Hood) and Tamerlan Tsarnaev and somehow still missed the key point: The fact that the intelligence agencies were able to know anything at all means that what they're doing is working. In fact the only thing that had kept those agencies from taking early action was our civil liberties and the need to employ due process, and the fact that there are still too many false positives.

Can a system like PRISM reduce the false positive rate? (Probably not, for domestic terrorists-to-be). If so, is it worth it? The answer might be "No", but it might be "Yes", too.

Another point to consider: If the intelligence agencies were able to get intel on the worst case scenarios (essentially "lone worf" budding terrorists) then how effective have they been in situations that play more to their strengths (which is to say, identifying and disrupting "cells" before they can proceed with an attack).

Sen. Udall has said that PRISM is completely redundant in stopping these attacks, but that doesn't mesh well with PRISM's prominent usage in the President's Daily Briefings. If PRISM isn't actually redundant, how useful does it have to be before we think it would be worth using?