The hilarious thing about conspiracy theories in general is conspiracy theorists: if you can honestly believe that an organization as vast, mismanaged, and generally systemically incompetent as a federal government can successful maintain the operational security necessary to pull off even a moderate sized conspiracy - to say nothing of 9/11, chemtrails, Sandy Hook, etc etc and all the other bull**** various 'truthers' throw around - then I have some ocean front property for sale in Alberta for a steal of a deal. Just send me the cheque in advance.
PRISM, etc don't count. For one, that's not a conspiracy, its an operational program within the NSA subject to oversight - and it was blown open by a private contractor, of all things, just proving my above point.
Conspiracy theory is just the latest manifestation of a very old aspect of human psychology - the need to believe that there are things greater than our daily lives, and that these things are non-random and rationally operating. Basically, it's the notion that some people believe existence is supposed to be ordered and make sense, which makes them readily accepting of anything that organizes non-related events into connected patterns. And it routinely makes me mock them for it. I class people who believe in nefarious government motives for legislation (e.g. "they'll make a gun owners get licenses so they can track and then take away all the guns and then no one can rise up against the evil government") in pretty much the same category, because it's barely a trip, nevermind a short step, from that way of thinking into full-blown conspiracy lunacy.