NSA frustrated by ability to collect data on only 20% of US calls

Siobahn Gorman for The Wall Street Journal:

In fact, it collects data for about 20% or less of that data, primarily because it doesn’t cover records for most cellphones, the fastest growth in telephony and an area where the agency has struggled to keep pace, according to several people familiar with the program.

The dwindling coverage suggests the NSA’s program is less pervasive than widely believed and also less useful. link

I find the NSA ’s inability to spy on all of us due to either not being able to obtain records or a legal snafu concerning location data so oddly unreassuring. I’m not sure if its because of their all but stated frustration due to the above, or because I simply don’t believe it.