We track user traffic patterns throughout all of our sites. However, we do not correlate this information with data about individual users. We do break down overall usage statistics according to a user's domain name, browser type, and MIME type by reading this information from the browser string (information contained in every user's browser).
We use tracking information to determine which areas of our sites users like and don't like based on traffic to those areas. We do not track what individual users read, but rather how well each page performs overall. This helps us continue to build a better service for you.