Algorithms to detect swindles on e-commerce websites?

Usually, I spend some of my time on e-commerce websites (we have leboncoin in France for instance) looking for the latest sales. I'm usually interested in technology products (smartphones, slates, computers, graphic cards) or furnitures (since I moved to a new city recently). Unfortunately, there are a lot of people who try to swindle the buyers. I'm sure you've already seen iPhones 3gs 64Gb sold at a very low price (250$ for instance). If you're into technology you're certainly aware that those are fakes (especially when it involves payment through Western Union). But imagine a non-aware guy who buys for the first time on the internet? So, we need to find solutions to this problem!

Imagine that you want to create a new e-commerce website, your only chance to survive is to propose a risk free ecosystem where you can tell your users that 99% of the sales there are OK!

How are you going to do it? Brainstorm!

I can give you few personal thoughts to start:

• Most easy way. The users moderate the content.

• An algorithm browses the web to determine if an announce is a swindle or not. What about a website that mashups all the known hoaxes and provides them through a REST or SOAP API?.

• Adding a set of rules to accept or reject an announcement. For instance this one can be rejected: iPhone 3Gs, 32Gb 250€. We can have, by the way, more sophisticated formula but you got the idea. In the case where an announcement is being classified as doubtful, by the previous algorithm, we can ask for more information about the seller including: a phone number, a physical adress or an ident card.

What are your thoughts?