One at a time, sure, ask the companies. But are you going to write an algorithm to ask every single company in the US about every single possible crime? What would you then do with that information? It would be a ridiculous amount of false positives and innocent people getting privacy and rights thrown by the wayside. I think that's what he's getting at...
Exactly, thanks for stating it more clearly than I did. The NSA isn't claiming credible evidence of a specific threat to justify this for a limited period of time – they're collecting everything and sifting through it, in order to try to prevent harm caused by an open-ended and non-specific threat.
https://en.wikipedia.org/wiki/False_positive_paradox