My Domain Stats is a FREE tool for checking and validating some of the most important metrics of a Domain Name.
The Traffic Estimation doesn't have direct access to DNS data or Access logs. It is based on a statistical model that tries to extrapolate the existing traffic for a Domain, based solely on the metrics presented.
The Appraise Formula needs also to be improved since it isn't able to quantify a Domain value considering subjective factors such as the name. For instance... ibm.com can be as valuable as xzq.com. Nonsense, of course...
Hopefully, with you contribution these models will be improved over time.