I think people worry too much about feedback - I've got 1886 in total, I think maybe 6 of those are negative, 3 from the same person(!) as a retaliation when I reported him to trading standards, anyway what percentage of 1800 is 6? Bugger all really. On one ocassion the neg was deserved because I didn't pay the person for some reason, and I left them feedback apologising. But when it's not your fault and you've actually tried to sort it, you have to fight fire with fire and tell them whatever feedback they leave you, you'll do the same.
As for the thieves and con men, the worst of the lot are the sellers of designer clothing. If you type in Prada or Stone Island or Wranglers, you'll find 95% are "BNWT" (brand new with tags), for s start half of these tags are the wrong colours, the clothes are in designs that the real companies don't make, yet they still ask ££££££ for them. I always read the feedbacks on clothes sellers.
Otherwise I wouldn't look as smart as this would I?