Although toolbars do contribute to the Compete community, they are only one of many sources of information. We believe that the variety in our sources helps eliminate any bias that shows up in a single source and helps to give a better representation of the average U.S. internet consumer.Jay Meattle from Compete.com explains in a follow-up email:
Compete aggregates data from Internet Service Providers, ASPs, opt-in panels, and Compete software – such as the toolbar and Firefox extension. We like to think it’s a better approach than Alexa’s, and pretty much any other provider of 3rd party competitive stats.
Cheers Andy and Jay.