My position is this. If a company/person who is owner of a forum is able or going to access Private Messages, such practice shall be made public within site's Terms. Personally, I think its a little over the top to be accessing private communications. However, a forum is private property and the rules can serve to protect the wants and needs of its owner. If one wants to venture in such procedure, users of the forum need to know about it beforehand.

Best,