One of the issues raging within the online world is the accuracy of statistics. There are so many ways to slice and dice the numbers, that it’s difficult to know whether any of them are on the mark. (See my Apples vs. Oranges vs. Plums vs. Pears post). comScore, which makes its living from providing online statistics, wades into the debate today with a study/marketing brochure looking at whether cookies are a valid tool to measure unique visitors to Web sites or the number of unique visitors that were served an ad by an ad server. comScore “discovered” that Web site server logs that use first-party cookies (which are left on a computer after it visits a Web site) can exaggerate the number of unique visitors by as much as 2.5X (or 150%). Question #1: what is comScore suggesting: that cookies are a bad way to measure unique visitors, or that anyone not using comScore’s service is making a mistake?