The NY Times is running a piece on the difficulty of counting the number of unique visitors to streaming video sites, like Hulu. Apparently, Nielsen's estimates of the total viewership for Hulu are far lower than that of other measurement firms.
Nielsen seems to be extending the model they use for tracking TV viewership to online video. In this case, they monitor the online viewing habits of some 200,000 users and weight them to extrapolate the total viewership of the site. This is clearly error-prone and potentially leads to substantial bias in the reported results.
I don't understand why Hulu does not simply track the number of unique users to their site directly, using IP addresses and cookies -- just like most other websites. Hulu should have all of the information it needs at its fingertips; why get Nielsen in the loop? I recognize that tracking IPs and cookies not a perfect approach, but I am surprised that Hulu needs to rely on a third party ratings company for its metrics when there are well-established technical solutions out there. The only guess I have is that it's to ensure that the ratings numbers can be independently verified, but there must be a better way than tracking viewership of a relatively tiny slice of the population. Can someone explain this?