>> Things like search warrants? What has been described in the PRISM slides is a interface in which a NSA agent can access a subject's data at will, in a few clicks and an affirmation that "yes, this person is a terrorist".

I'm not sure where you getting that from the slides. They don't explain how an analyst uses the system.

>>Google has officially denied being a part of PRISM. The way you phrased this statement makes it sound like the OP is sneakily leaving out the PRISM implementation, which would be sneaky if Google were a part of PRISM.

Other media reports from insiders (not information on the leaked slides) make it sound like PRISM is more of an NSA internal thing that aggregates data and presents it to analysts. Based on the description of the slides it sounds like the NSA has some integration with the on site premises of the target company.

So it could be as simple as PRISM is just a way of automating the whole process of getting data from a valid warrant which would be consistent with the denials made tech companies. They don't have any contact with 'PRISM' per se; they have just set up their systems to spit out data when they get a valid warrant.