The question is not about APIs for apps; the issue is that a user cannot readily export their complete social graph from Facebook--specifically, in a way that allows them to rebuild it elsewhere in its entirety. It's trivial to easily provide that capability in a way that wouldn't expose it to apps. And obviously Facebook doesn't have an issue with sharing the data, because it's available through things like Yahoo email. However, nothing exists to make it easy for a user to retrieve it. And when something like a third-party browser extension provides the capability, Facebook seems to intentionally break it.

It seems the only reason for this is because Facebook wants to make it hard for users to leave, unless you know of some other explanation?