[jlgreco]

Well, we also don't know if PRISM is piggybacking on another, possibly far more expensive system (the hypothetical hardware could already be in place, and under the budget of another far more expensive program).

Really, we just don't know. We don't know anything, except that it sure seems that something is going on. The documents are not getting the same treatment as the fabricated documents of a raving lunatic anonymous coward on Slashdot.

It seems fairly prudent to assume the worse case scenario, better safe than sorry, but it is important to not confuse that assumption with knowledge.