What 10 links would a hypothetically perfect search engine return for that query?
Edit: Judging from the replies, many of you seem to think my question was "how many ads would a perfect search engine show?" Please note that this is not what I asked.
Edit: Judging by your edit, you seem to be confusing "what should they show" with the original question, which is something like "Why is the right 50% plus the top block of the left column ads?"
The answer to your question is "whatever links match the search terms based on their wonderful, wonderful indexing algorithm."
The difference is that one is what Google think will be the most useful results for users, and the other is what Google think will make them the most money regardless of usefulness.
The "hypothetically perfect search" has absolutely zero ads and only shows results based on merit, not how much somebody was willing to pay. Why is that so hard to understand for Google employees? Your founders wrote a bit about this back in the day you know:
Currently, the predominant business model for commercial search engines is advertising. The goals of the advertising business model do not always correspond to providing quality search to users. For example, in our prototype search engine one of the top results for cellular phone is "The Effect of Cellular Phone Use Upon Driver Attention", a study which explains in great detail the distractions and risk associated with conversing on a cell phone while driving. This search result came up first because of its high importance as judged by the PageRank algorithm, an approximation of citation importance on the web [Page, 98]. It is clear that a search engine which was taking money for showing cellular phone ads would have difficulty justifying the page that our system returned to its paying advertisers. For this type of reason and historical experience with other media [Bagdikian 83], we expect that advertising funded search engines will be inherently biased towards the advertisers and away from the needs of the consumers.
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. 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.
Language is the biggest influencing factor, at least for me.
I get zero ads if I search for “trash can” but an ridiculous amount of ads if I search for “Mülltonne” (German for “trash can”), all because I’m searching on http://google.de/.
Also, it depends on what country Google have geo-located you as being in and not on what country's Google page you're searching from; non-Americans get completely different search results on Google.com from Americans.
What ads you see will vary a lot by location. For example here in the UK 'trash can' returns no ads at all for me. On the other hand 'rubbish bin' results in a page with 8 visible ads and only 3 visible organic search results: http://i.imgur.com/7frlR2J.png
For any query less and less percentage of first page is dedicate to organic example.
E.g. a silly example: https://www.google.com/search?q=trash+can 25-30% organic, rest are the adds.