It will be very hard to enforce. You can always accidentally 'lose' your phone or computer which contains those pictures. Then someone would 'inadvertently' post those pictures somewhere just for fun. It will be hard to prove that it is for revenge.
It also has an added bonus that you now have a written proof of the conversions in the email trail. So they cannot deny that they never said this or that. It is important in some sectors of the corporate world.