Whatever their reasoning (and someone over on MLC said that they thought it was so we wouldn't exchange personal contact information [like it's so hard to look people up on FB anyway?], and then quickly delete it, but who knows. And if you THINK about it, isn't it far more likely that NOW someone might accidentally post something dangerous, and not be able to delete it? An accidental slip of their child's real name, or their spouse's, or some such?
I agree. And I'm not on FB so I can't relate to that but my goodness I am a Grammar Queen and it drives me mad not being able to edit my miss-iwueopruwer-pellings.