Case by case is the way.
Plus people can use multiple identifies, real and anonymous. 
I think people naturally choose to expose their identity, because they want recognition, fame, validation.
If they don't, they have reasons for that :).
In my case there are a few. 
I also have accounts with my real identity on different social media platforms, but there, when I rarely post, I don't mention anything related to what I post here. That guy is someone else...