I'm not sure though if that has to be the case though. Some contract types terminate automatically, question is if that is only legally possible for those special cases or if any contract can be written that way. Similarly if data deletion clauses could be challenged or not - being party to a contract that says all data has to be wiped if person X dies doesn't help you with gaining access to that data. That of course isn't part of the current social media user agreements, but could very well be added now as an option.