eMarketer.com’s report estimates that the big 4 will account for 66.6% on online advertising revenue in 2007.

      2004 2007
    Google 13.1% 32.1%
    Yahoo! 18.4% 18.7%
    AOL 6.8% 9.1%
    MSN 9.4% 6.8%
    Total: 47.7% 66.6%

Even without Google , the remaining 3 still account for 1/3 of the internet ad spend total.