Just my pov, but i gotta say if i knew i was gonna scam someone for anything over £20 then a one off payment of £5 is nothing. Id pay it if i was a scammer.
Personally i think unless you lock it down crazy levels then you are never going to beat it, and it would be better to not have a trade section, and just let people use ebay instead. Sure you have fees, but at least you get protection of some form.
Assuming the trade section will stay i would say:
- Ban listing items are buyer pays fees or gift
- Pictures in adverts must have bit of paper showing name, username, and date
- Postage tracking numbers must be provided - no standard postage
Even then, policing the section would be a full time job, and Jimmy etc give enough time to this site, they cant be expected to do that as well.