Wired: Web Industry Still Flies Blind

They may wear very, very serious facial expressions and talk about methodologies and data integrity, but the way that syndicated research companies measure site traffic is seriously flawed. Wired reports that comScore and Nielsen, using roughly the same sort of mechanism to measure traffic, can't generate estimates that are within 70 percent of one another.

To some degree, this has been a deliberately ignored problem among media buyers in the industry because gross measurements like site traffic do not hold the same importance they do in traditional media. A print ad, for instance, would have to run in all issues of a publication, making the circulation figure the same as the ad exposure figure, which is far from true online. But the gross circulation figures do factor into reach and frequency calculations, and their squirrelliness raises questions about other information coming from the companies that employ panels to reach findings.