Saw the 60 Minutes slow-pitch softball game on this yesterday evening. The NSA via CBS carefully stated that they only actually collected and used the cell call metadata. That was one of those things that is technically true as far as it goes, but not true at all in a real-world, common-sense way.
What the NSA means when they say that is that they actually capture EVERYTHING in the call, but do not review or analyze anything but the metadata unless and until they are either told to by another agency (Presumably based on probable cause and with at least a claim the other agency really got a FISA warrant) or they develop probable cause and obtain a FISA warrant to do that themselves, for instance based on their call network constructs linking a given number to an on-going investigation.
Legally, what they are doing IS a seizure, the fact that they grab all the call contents is still a seizure whether they review it at the time they seize it or not.
There is, of course, no oversight, counterbalance, or check whatsoever on their claim to only review said information based on probable cause, since the FISA Court has no power to intervene and investigate, as it is only able to review matters the Administration decides to bring to its attention.