Re: A weaker system
You're spot on. And don't worry, they aren't storing MP3s. That huge complex in Utah (and Fort Meade, elsewhere) is analyzing the speech, pictures, etc. and rendering machine-friendly-for-harvesting representations of the information. This is what google voice has done for a while also.
So if some lackey from the govt says "we don't collect voice records" it just means that the waveforms have been rendered into something much more analyzable.