On DDG, "dragon book !amazon" lands me on an Amazon search result page.

Very different. By adding one !, I saved a whole page load and render, and having to click on a result.

I guess you're arguing that Google's search is better than Amazon's. In some ways, assuming that you're looking for the compilers book, it is. I'd argue that it doesn't show cover thumbnails and stuff like that, so it's a toss up. But this is one example out of many. I think the wikipedia bang is very useful, for example.