This interesting set of observations points to the notion that Congress has authorized the NSA to suck up the entire Internet, filter everything for key words, and examine anything that is caught by the filters.

Does that mean content filtering is ruled out altogether as an investigative technique? Kris thinks the agencies might have a "decent chance of pulling that off constitutionally if a judge approved the search terms." 

When the Bush administration finally consented to submit its surveillance program to the supervision of the FISA court, it cited recent legal developments that.. gave the Court's imprimatur to "anticipatory warrants"—in other words, warrants sketching out abstract conditions that, if satisfied, would constitute probable cause for a search.

That would dovetail with the pointed omission in the FISA Amendments Act of language requiring that surveillance orders describe a "specific" target—meaning some particular individual implicated in terrorism, whether or not his name is known, as opposed to a series of general traits or properties that would constitute grounds for considering anyone a terrorist suspect. All this suggests an attempt to shift toward a surveillance regime in which huge quantities of data are "filtered" but only those that trip the computer's alarm bells are "acquired."