One of the most frustrating things about the NSA and FBI's domestic spying practices is that we don't really know how far their programs go. Maybe it's not as bad as we all think it is, but the truth is it's probably worse. We just don't know. The NSA might not even know!
Those government agencies obviously have their reasons for keeping their spying programs under wraps, but the last time I checked, we live in a democracy of the people, for the people and by the people. We can't protect our Constitutional rights when we're not even allowed to know when they're being trampled on.
That's why Twitter is suing the federal government. It wants you to know exactly how much information the FISA (Foreign Intelligence Surveillance Act) courts and national security letters compel it to hand over.
Many tech giants that collect our personal info are in the same boat. Google, Facebook, Microsoft, Yahoo and others are on record as being against these types of secret requests for information, but the laws force them to turn over certain information under FISA or national security letters.