I don't understand the outrage here, aren't gag orders pretty much standard police tool? I mean, if you are taping the new Al Capone/Ben Laden/Ted Bundy, then surely you don't want Twitter to reveal it no?
Even the above is not as much of a concern - but the same mechanism can silence the providere about more drastic intrusions which compromise the whole service - such as coercing private encryption keys. Lookup the whole Lavabit thing.
You then decide if you care. If you do care you instLl and carefully use encryption software and keep your private keys under your control.