I just wanted to clarify your point about comparing Gtrends data to other services. We’ve been watching these things closely as they develop and to be honest, both the underlying data sources, and the way Google is arriving at their final numbers is the most blackbox approach in the 3rd party analytics space. The triangulation approach (internal search data, google analytics, 3rd party, and (potentially) toolbar data) they are taking can - and very well may - lead to really robust data.

But without knowing how they are doing it, how often they update their monthly reported data, and where the data is coming from, its really difficult to trust either of these new tools. At least with Alexa I know that everything skews towards webmasters/techies, and with Quantcast I can look at “Quantified” numbers and have a pretty good idea of what actual traffic is.

For the record, we use a combination of 3rd party, clickstream based data (ISP, ASP, Toolbar, Plugin, panel data).