+1"You may only post a for sale thread, or reply to a wanted thread, if you are a site supporter"
Further info; http://www.civinfo.com/forum/sale-wanted/1257-trading-rules.html
This was a move forced on us by fraudulent people who would just come here to advertise an expensive item, insist on a Paypal gift payment then no more heard.
Paying to be a supporter isn't foolproof but it seems to have helped.
All we can advise is watch the history (first post for example) when purchasing expensive items.