According to comScore, in June 2006, the monthly share of online searches were distributed as follows:

Google Sites: 44.7%
Yahoo! Sites: 28.5%

Those two engines account for 73.2% of all search traffic.

When considering where you are going to spend resources implementing a search marketing campaign, keep the numbers above in mind.

There is another 26.8% out there that are searching across hundreds of smaller engines, but chasing those visitors, in most cases, is not worth the time and effort. The amount of time you put into setting up campaigns on the smaller engines vs. the value you generate from those efforts usually don’t add up in a positive way.

Stick with promoting your site on the big two (Google and Yahoo!) and you’ll be maximizing your time and resources and generating the best traffic to your site.