john keegan dot org

From SEOmoz | Know Your Playing Field: The Real Top 100 Domains:

• 60% of the top 25 domains are controlled by an elite six.
• 43% of the top 100 domains are controlled by an elite dozen.
• Together this elite dozen drives more than 1.3 billion monthly unique visits.

A must read… FYI, the list of top 100 domains is available here:

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• NUMBERS