Not sure why you're getting downvoted. I don't know about the 100% part, but it doesn't seem crazy or impossible that they'll do something like that, and we should all be well aware of the possibility.
He is getting downvoted by the folks who either 1) know this is true or 2) who will deny this is true even if it is true. And I will burn a bit of my karma for this comment too... :-)
You would hope that the NSA would only have tools to collect the messages of targeted users, but seeing their other programs, Id assume they just dragnet everybody.