An important thing to know here is how compartmentalization works. On one hand, it's to help limit classified information to those with a need-to-know. On the

An important thing to know here is how compartmentalization works. On one hand, it's to help limit classified information to those with a need-to-know. On the other hand, it's used to mislead oversight and limit the visible scope of an overall goal. So while it may be technically true that PRISM is only doing x, there may be a separate compartment (called, say FROGBUTT or whatever) that performs the sister role of y in support of PRISM. This is how intelligence agencies hide and mislead the public. They say "Yeah, we do have a program called FROGBUTT that collects call metadata, but we don't collect personal information or examine the contents of a call." What they don't mention is that they have another companion program called LIZARDDICK that does collect that accompanying personal information, and they have yet another program called COWBONG that collects the contents of calls. This is how this work. Plausible deniability, onion layers, confusion. Combine this with the fact they periodically change compartment program names, and it gets exponential. See also: RAGTIME, THINTHREAD, STELLAR WIND, TRAILBLAZER, etc