[mpyne]

The point of PRISM is that if you already have a person of interest in mind, you can data mine within that persons's communications, likes, pages read, etc. to determine if he/she is actually being 'radicalized', or if they have connections to other people who are 'radicalized'.

From there you can determine "who's who in the zoo" of extremist cells for use in other intelligence collection schemes. E.g. if someone receives messages from known intermediaries of an AQ bomb makers and then 'drops off the grid' it may be a good time to step up to video/satellite surveillance.

Simply doing random searches isn't tracked by PRISM (though it might be from systems that use wiretap features). But even random searches like those are likely to simply be filtered out outright by the NSA, they are simply too common (even without pranksters who run the search thinking they're Sticking It to The Man) to be worth following up individually.

Even the NSA doesn't have infinite resources after all, and they are still dependent on other agencies for follow-up activities, and those other agencies are certainly more resource-constrained than NSA is.