from Attributor Blog
"December 18, 2008 @ 8:00 am
The Google ad serving juggernaut appears secure even if Microsoft and Yahoo agree on a deal to merge their search advertising businesses. Our analysis of ad server calls across 75 million domains shows that both Yahoo and Microsoft lost significant share compared to our March report and now make up less than 15% of the total market.
The explosion of new ad networks in 2008 had an impact, but only one newcomer - Revenue Science- broke into the top 5. Unsurprisingly, Google’s AdSense is dominant on smaller sites while Google-owned DoubleClick leads on larger sites; however AdSense made great strides on larger sites, leapfrogging Yahoo into 2nd place."