Dropbox better come out ASAP with a formal response to this. But honestly, it might not even matter because if the NSA has targeted Dropbox, any betting man would say that it is already part of the problem.
If Dropbox is handed a National Security Letter (NSL), unless they want to go to Federal prison their people have no choice but to lie about it.
Look at some of the discussions where these companies' carefully worded denials are parsed, they aren't really denying it. E.g. "back doors" aren't an issue when a NSL is used to come through the front door.
Dropbox better come out ASAP with a formal response to this. But honestly, it might not even matter because if the NSA has targeted Dropbox, any betting man would say that it is already part of the problem.
Ugh...