I have my settings in a similar fashion - only to accept PMs and Visitor messages from folks on my contact list.
Although I daresay admin/mods override that setting for good reason.
I think staff always has the option to PM or message you. I have my wall set so that only my contacts can post on it. Too many "problems" being discussed in lengthy fashion on my wall...so now I've got it where it has to be discussed by PM unless you're on my contact list.