A thread at WebmasterWorld brought this to my attention.
Conduct a search on overture at Google.com (click on the bold link), and you won't find overture's Web site in the main search results. In fact, Brett_Tabke says that Overture "bans all indexing via robots.txt" and Google just obeys the robot.txt file. Why does Overture disallow all indexing by the robots? Brett suggests "Don't you think that having your competitors bot crawling all over your website is a bit creepy?" I feel Brett is joking with this response, let me try to give my own opinion on why they are disallowing organic robots.
Overture is an advertising company based on mostly the pay per click revenue model. What do they have to lose by allowing Google or other engines from indexing their site? I don't see anything. Can it be a matter of principle? A PPC company should show its customers that organic (free/natural) results are not as effective as PPC/Paid results? By them disallowing organic robots from crawling and indexing its site, they are making a strong statement that PPC is where it is at!
Oh, but Yahoo! owns Overture, and Yahoo! has their own organic search engine. Well still, they are separate divisions with unique missions. In fact, if you do a search on overtue in Yahoo! you will find overture.com listed. Well, if you look closely, that is a form of Overture's Site Match - overture's pay for inclusion and cost per click program that works with Yahoo. So it is a form of paid advertising, which overture supports.