I remember a time when ads were clearly on the sidebar of Google's search results so users wouldn't mix them up with the actual search results and unintentional

I remember a time when ads were clearly on the sidebar of Google's search results so users wouldn't mix them up with the actual search results and unintentionally click them. Then somebody at Google realized that if they moved the search results into the middle of the search result, then a lot more users would mix them up with the search results and click them. I'm sure it increased click-though rates by a lot.