From what I've learned, psychiatrists, therapists, teachers, lawyers - anyone who deals with the public in a professional manner - are advised to have very private profiles on social media. They should allow the public to see what they are ok with sharing. T's with loose boundaries seem to have difficulty in this area (I've come across teachers who do too). My daughter's kindergarten teacher got fired for something she posted publicly on facebook about a student. Yes it was stupid, but she was older and not well versed in social media - meaning she probably didn't know everyone could see what she posted. Still, if she didn't have many of her student's parents as "friends", it might not have been an issue.

I think the biggest issues are personal safety and/or conflict of interest. When I become a T, I'll stay away from facebook or other social media unless it is a page for clients.