Yeah, darn good idea here! Perhaps in a larger size font:
" For your protection, be advised that this site has NO control over usage by it's members. It is YOUR responsibility and YOURS ALONE to make sure that you do NOT respond to offers, requests to purchase or any and all un-solicited emails from ANYONE purporting to be a member of this Forum!" (Any questions regarding this admonishment should be made to an Administrator).

How does that sound?
Lloyd