Think about the heterogeneity of the data, the lack of structure, and the unpredictable nature of its generation. Frankly, I have no doubt that the NSA is not monitoring phone chatter on a mass scale, probably not because they can't, but because if they did there would be no way in hell to parse, store, process and evaluate the data generated.
We (the scientific/big data community) can barely get recommendation engines working well - engines which have one set of data (what you watched) and do one other thing (suggest what else you might want to watch). Unless the NSA is decades ahead in a number of fields (like data warehousing, statistical analysis of massive datasets, machine learning) how are they getting useful information in a systematic way, considering the pressure from the data-firehouse involved?
My guess is they're probably not - instead the data are collected, and then used in conjunction with traditional approaches. e.g. little johnny buys some fertilizer and one way plane ticket - so who's he been talking to, what's he been saying, etc.
Honestly, how the NSA is using/dealing with/storing/accessing these data is actually an incredibly interesting question, from an academic/systems perspective.