Anecdotally I heard about some of the conversations with the government and adult industry regarding the UK porn filter. It was something along the lines of: Industry: "OK, we get you want to put a block in front of adult sites. But what about all the porn Twitter?" Govt: "There's porn on Twitter?"
When we're all getting angry about encryption and privacy and backdoors (and whatever else), it's probably prudent to remember these are the kind of people we're dealing with.