Here is the process of this scam, next time you see any of these signs you should stop negotiations (or not start them at all)
1. He will contact you usually pretending to be a CEO of a company, showing very much interest in a name.
2. You reply, he may reply back, he will usually mention an appraisal as a way of establishing a sales price, at this point, he may or may not give you directions on where to find a "trustworthy" appraisal service.
3. In his 3rd email he will definitely suggest what he considers trustworthy appraisal services (if he hasnt done so in his 2nd email), and he will do it in a rather clever way. He will not suggest one direcly, but he will give you a link to a fake forum thread, where people supposedly discuss about domain appraisal services (usually the ones leading the conversation have usernames that evoke trust, like Dr. Holmes etc). In that fake thread, they will mention a few of the usual services like Sedo, but also talk about some other services you have never heard of and the purpose of the entire thread is to make you believe that these other services are in fact better than sedo and are as trustworthy as such a service can get. These sites are operated by the scammers, and if you fall into this scam you will order an appraisal, they might or might not reply with one, but the important thing is that the buyer will never get back to you after that. His goal was just to make you pay them $40 or so for the appraisal.
Here is an example of one of the many fake threads they use :
http://discussnames.007sites.com/Archive/703581.htm
Notice how they promote
http://www.DomainExplorer.org , which is their scam service
