That's a good question, and something I've spent much time on. Cuil (2008-2010) tried. I knew some of those people. It cost them about $30 million to launch a full scale search engine. They had no revenue model. In retrospect, they were hoping to be acquired by somebody. It was some ex-Google people, trying to replicate older Google technology. They had a great launch, but the system wasn't very good and traffic rapi…
When someone sees a search ad, they're actively looking for the item of interest and may be ready to buy. My experience with Google is the opposite of this. When people are searching google they are looking for information. When people go to Amazon they have their credit card in their hand. Most of my google-ad clicks (85% last check) are clearly not interested in buying what they are looking for. They are only on my…
And – as just another anecdote – I have had continuing success over the last 8 to 10 years with search ads, while not having a single conversion with anything else (Facebook, youtube, twitter etc.) as far as I can tell.