@chu I had a similar jolt of disbelief when I talked to a company director on parental leave about the Snowden revelations.
Intercepting, archiving and mining packet switched communications is undetectable and cheap for a nation state. At the time of that conversation, I had lived for more than a decade with the assumption that every government with internet access was already doing this. To hear an informed intelligent person's surprise at hearing that the US was doing this was startling.