I had one of these a little while ago (I think they just wanted a domain without paying), luckily I googled the email address and noticed a large "don't trust this site/person" site.
I have had this multiple times. They are normally very serious sounding people like they actually want to buy it. Someone i knew for a long time but after awhile he admitted that he was trying to scam me out of 300$ for an apraisal at his site!!!
this is happing a lot, one of the things to look out for is the e mail address.lets say tom<at>somedomain.com go to somedomain.com and you will find its a free e mail address but usually the crap site they want the appraisal done by would be enough to but you off,