Why Yahoo took this long to release a native iPhone app for its search engine is a mystery. Yet, it's a significant day for the iPhone since the release of Yahoo Search app for the iPhone finally completes the triumvirate of the major search engines for the iPhone.  Google has long been in the Apps Store while Microsoft's Bing recently got an update. And while both Google and Bing tried to include as much nifty features as they want in their respective iPhone apps,