Non-exportable data is pretty much the definition of a lock-in. There's essentially nothing that's impossible to walk away from, so the only thing worth considering is getting out what you put in.

In terms of a social application, it's legitimately harder to make a not-locked-in service. Who owns what, and how much of it is valid when you transfer data to another host? But it's still a lock-in, because there's no way to leave and retain things.

Imagine if your phone would only export contacts to a new phone if you stayed with your provider. Sure, you can still leave, but a data-lock-in is still a lock-in technique.