[adwords.google.com...]
Ad Sitelinks can appear in four different formats: three-line, two-line, one-line, and embedded:
Three-line and two-line formats: Sitelinks are designed to trigger in situations where an ad provides the ideal answer for a search query. These ads are most likely to trigger on unique brand terms.
One-line format: Sitelinks will trigger with more generic terms, but may also include brand terms.
Embedded format: Sitelinks will trigger whenever your ad qualifies to appear above the search results and the text in your ad exactly matches one or more of your Sitelinks.
Why is it bad news for those that are ranked in the top 3 specifically?
Since it is very difficult even for experts to evaluate search engines, search engine bias is particularly insidious. A good example was OpenText, which was reported to be selling companies the right to be listed at the top of the search results for particular queries [Marchiori 97]. This type of bias is much more insidious than advertising, because it is not clear who "deserves" to be there, and who is willing to pay money to be listed. This business model resulted in an uproar, and OpenText has ceased to be a viable search engine.
But less blatant bias are likely to be tolerated by the market. For example, a search engine could add a small factor to search results from "friendly" companies, and subtract a factor from results from competitors. This type of bias is very difficult to detect but could still have a significant effect on the market. Furthermore, advertising income often provides an incentive to provide poor quality search results. ....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.