Now your private info is public.
Now your private info is public.
If anybody knows (and has experience) well enough about keeping data safe (indeed through doing quite the opposite), it's these guys. Whilst it's well established that in software there's not much we can do to avoid bugs and other vulnerabilities, there's rather something to be said for practical operational security in making it almost impossible for data of this form (and especially volume) to be leaked - good luck trying to get data across an air gap or indeed something monitored physically to the extent that this all is.
(caveat: spies and other infiltrators would perhaps, in certain circumstances be in a position to leak this sort of stuff - there is only so much that can be done to avoid this, of course (oh - and also others on the inside willing to leak information))
Also it's not just NSA doing this. Maybe in the US, but I assume that in Europe there are many similar centralized government databases full of information about people. And Asia.
The point is, given enough time the shit will hit the fan somewhere. No matter what. Don't try to deny this.
Also, whilst they undoubtedly keep data around awhile, it's not kept indefinitely, surely - it has a shelf life after all. Whilst someone might get this stuff wrong in the future, again, surely that would come about most likely due to some discontinuity in this process (like if they were forced to stop awhile and then continued, losing operational details in the process).
Also once again, I would guess that those with intent to cause disruption, fear or harm (even dissent) would probably have an easier time of things a dozen other ways. In building secure systems, it's always worthwhile to gauge the value of some data to an attacker and the cost to them of obtaining it.
I'd be more worried about an employee leaking data. Most telcos have many many employees and a carefully planned leak would be difficult to detect and prevent. In one installation I was involved in, we had access to all SMS messages in the system, in realtime, before the recipients got them. It would have been pretty easy to copy them to a memory stick and then leak them sometime later.
Lots of "probably". Indeed the whole eavesdropping story should have been secret, but it seems like it leaked from the same people that decided to protect you.