Web optimization to other search engines

Do you think Google is the only one you're relying on? In terms of web optimizing? Search engines like Yahoo and Bing are behind Google's rankings, which of course needs their allies' optimizing techniques and tips to strengthen their popularity and services. For me, this is a great idea. Not only you ranked high and gaining huge traffic on Google, but also on Yahoo, Bing, Dogpile, Ask, Altavista, etc. They're worth to do web optimizing there.