Because you still need the user's willfull cooperation. It doesn't work if the user doesn't cooperate or if he's not supposed to be aware that he is being listened to, which is I believe the case in most terrorism cases.
Not always, especially when law enforcement can request data straight from the provider, which I would imagine happens in the majority of internet crime investigations. Because let's be real, how many internet companies have a zero knowledge policy towards their users' data?
> Because let's be real, how many internet companies have a zero knowledge policy towards their users' data?
Well, the whole point of TFA is that Apple, Google, Yahoo and the likes want to progressively move in that direction (not totally for sure, but just enough so that the FBI/NSA doesn't like it).
Not always, especially when law enforcement can request data straight from the provider, which I would imagine happens in the majority of internet crime investigations. Because let's be real, how many internet companies have a zero knowledge policy towards their users' data?