Shown below is a monthly survey of traffic data for the top 25 largest web 2.0 sites ranked by a combination of Compete and Quantcast data. For each site, unique U.S. monthly visitor data as well as respective rank is showed. For entries where a wide range exists between the two data sets the highest numbers were used for ranking purposes. Although no traffic metrics are completely accurate you can believe the data below to be useful for gauging relative audience size.