Furthermore, advertising income often provides an incentive to provide poor quality search results. For example, we noticed a major search engine would not return a large airline's homepage when the airline's name was given as a query. It so happened that the airline had placed an expensive ad, linked to the query that was its name. A better search engine would not have required this ad, and possibly resulted in the loss of the revenue from the airline to the search engine. In general, it could be argued from the consumer point of view that the better the search engine is, the fewer advertisements will be needed for the consumer to find what they want. This of course erodes the advertising supported business model of the existing search engines. However, there will always be money from advertisers who want a customer to switch products, or have something that is genuinely new. But we believe the issue of advertising causes enough mixed incentives that it is crucial to have a competitive search engine that is transparent and in the academic realm.
http://infolab.stanford.edu/~backrub/google.html
The main difference seems to be that today even getting the top organic search result doesn't provide enough clicks for advertisers, so they feel obliged to purchase ads for their own brand names even when they already rank first. If people searching for Southwest Airlines on Google aren't ending up on the Southwest Airlines website without a huge great banner ad (despite it being ranked at the top of the results) then something is going badly wrong on the Google search results page.