Isn't it time the MN had a separate section for discussion of 'social media'?
The same old questions keep repeating in AIBU about 'should I post this?' and 'should my friend have posted that', with the same old answers. Often there are several similar threads running at the same time.
A dedicated section would hopefully have the answers all in the same place and allow the love FB /hate FB arguments to go on and on...
Most threads about social media are generally about relationships and communication between people - the medium through which the communication happened is not always relevant, and it's generally not the main point of the discussion.
If people are actually talking about whether someone is being unreasonable then I don't see why it shouldn't be in AIBU (and I am generally very anti "things being in AIBU that shouldn't be")
I agree that "is it right to post pictures of children on Facebook?" or similar really are about social media and the internet.