Working in the web marketing statistics business, I know how difficult it is to produce reliable statistics about visitors and their actions. A good web stat application, whether it is behavioral or marketing related, has to make good decisions all the time to produce correct, uniform, and reliable statistics. It takes constant monitoring and adjustments and also has to be build with intelligence for self maintenance. It also has to make decisions about fraud and various browsers and platforms. To summarize; it’s a very, very difficult discipline.