So, the first thing you need to understand is that
over half of users can't distinguish the ads from the organic results:
https://www.stateofdigital.com/adwords-vs-organic-difference...So if you look at the Appendix example below,
> 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
...That is actually what Google itself is doing today, in a very real and practical sense. They claim it's different because ads aren't search results, but since users can't tell the difference anymore, the result is the same.
Another example in the Appendix is about trademark squatting:
> 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.
Google does a slightly modified version of this too: It places competitors' ads above the real result for the airline's brand. This means that, in order for the airline to be the "top result" for it's own brand name, it has to pay Google for an ad that Larry and Sergey conclude "shouldn't be required".
If you search for "best buy" on Google and aren't blocking ads, you'll notice the ad at the top is a Best Buy ad. There's no good reason they should have to buy that ad, because they're obviously the best result, the user already knew what they were looking for. But if you want to be the "top result" on Google search, you have to pay for it now.
And we've hit that mixed motivation issue with an ad-based search engine: Google makes a lot of money when you click an ad. It doesn't make a lot of money when you click the organic search results. So Google has a huge incentive to make the ads look like search results, which is why Google search ads now look nearly identical to search results.