On jill/text I cam across an interesting graph about OpenSocial vs. Facebook showing the difference in market share. Hitwise provides statistics and analysis of internet usage. They get their data from ISPs, which sounds like it could be a privacy issue. See their Product Features for the services they provide that most of us can’t afford. See what they say about how they gather information in How We Do It or here is quote from their press release on Hanah Montana Most Searched for Halloween Costume:
Since 1997, Hitwise has pioneered a unique, network-based approach to Internet measurement. Through relationships with ISPs around the world, Hitwise’s patented methodology anonymously captures the online usage, search and conversion behavior of 25 million Internet users. This unprecedented volume of Internet usage data is seamlessly integrated into an easy to use, web-based service, designed to help marketers better plan, implement and report on a range of online marketing programs.
They have blogs by their analysts, most of whom seem to be in the UK, that have interesting notes about trends like iTunes overtakes Free Music Downloads in Internet Searches.