Now that all four of the major search engines incorporate multimedia (or multi-vertical) content into their organic results, Danny Sullivan has deemed this new era of blended search, "Search 3.0" -- noting that it represents a time of great opportunity for the industry, and giving a detailed, illustrated account of how we made it this far.
So what was Search 1.0? It was searches by Lycos and Webcrawler, with ranking algorithms that focused primarily on the location and frequency of the words on each page. Users were able to find info on the rapidly expanding Web more accurately -- but the simple criteria led to an upsurge in keyword-stuffed pages.
Larry Page and Sergey Brin helped usher in Search 2.0, with their Google and its algorithm that focused on outside factors like links, as well as other off-page traits like domain age and time spent on the site. Still, Search 2.0 wasn't perfect -- as Webmasters and scammers alike figured out how to "work" the system by buying, selling and wrangling the links that could boost their rankings.
So Search 3.0 has made it easier for users to find information, whether it's an image, a video, a book excerpt or an ad -- and almost levels the playing field again for site owners (and SEOs), since there's a need to index and optimize all sorts of new content.