Apple has responded
http://www.apple.com/customer-letter/
The fact the FBI are trying to leverage a very old statute is what makes this scary. It opens the door for them to get access to any device they want. It's not a "this will be used on only this guy, trust us!" It's a build a master key to unlock any phone so we can use it when we like, there's no mention of needed an actual search warrant to do it either.