EDIT: I don't think that "innocent until proven guilty" should only apply to crimes. I think the same concept can and should be used in almost all cases of accusing a party of something.
Of course, even if you can't prove anything, it might be prudent to hedge against the possibilities by assuming everything is actually public, but given the sort of things people post publicly (to four thousand of their closest friends and confidants) on Facebook, that might be a pretty low bar.
The rest of us are watching all the signs for info to help us develop our own strategy in this not-so-theoretical game of prisoner's dilemma.
If FB received a FISA Sec. 702 order for the contents of nycterrorcell@facebook.com's account, and they disclosed that, that would presumably violate a court order and they would find themselves in contempt of court. For good reason: when there is an actual terrorist investigation (remember the terrorist threat is overhyped and you're more likely to get struck by lighting), you don't want to tip off the bad guys.
But aside from that very narrow non-disclosure exception, there is no threat to "put them on trial."
(I was mainly citing your article to establish the the gag order. First hit for https://duckduckgo.com/?q=facebook+gag+nsa )
If you, the recipient, want to challenge the order as invalid, you're free to do so, and there's an appeal process. I was the first to disclose two weeks ago that Google is fighting two national security orders in two different federal courts (SF and NYC). There have been other similar cases. A facial challenge to FISAA 702 (by Amnesty, not the provider) went all the way to the Supreme Court.
You really need to read the applicable laws. My articles link to them. Otherwise it's like talking about the details of mobile app development without knowing how to program.
http://webcache.googleusercontent.com/search?q=cache:http://...
(Note I'm not pretending to be a journalist here, just wearing my conspiracy hat today)
Sounds kind of tyrannical to me, but what do I know?
So disobeying a court order is contempt of court, but a judge can't throw you in jail without a hearing for it.
Source: http://en.wikipedia.org/wiki/Contempt_of_court#United_States