Isn't that how Facebook got started: by creating networks based around schools? I don't see the big deal, especially if the school isn't developing new communication tools for students.
Corporations aren't robots. They don't pull the plug on transportation infrastructure because of a TOS violation. There are plenty of disabled people who rely on Uber.
snapchat DMs are used by young people; think AIM. snapchat stories is an old-people product. It fits into their existing frameworks of social networks: public broadcasts.