It's official – the long awaited Yahoo-to-Bing transition has taken effect. Both Bing and Yahoo today announced that Yahoo's organic searches are now powered by Bing.

Shashi Seth, senior vice president of Yahoo search products, explains that Yahoo web, image and video searches on desktops and mobile devices are now powered by Bing. Indeed, when searchers type in a query on Yahoo, a line at the very bottom of the page clearly marks the results as "Powered by Bing."

At present, paid search campaigns for the two portals will remain separate, and Yahoo is making it clear it isn't abandoning search efforts in light of this transition. Seth explains that Yahoo will still be actively developing "immersive experiences that foster serendipitous discovery." This statement supports the claims of Ben Shahshahani, head of Search Science at Yahoo, that the search engine is moving toward contextual searches, which Brafton reported last week.

Bing officials seem to concur that this isn't a matter of one search engine overtaking the other – it is a "search alliance." In the Bing blog, officials say the primary goal for Microsoft and Yahoo is to "provide advertisers with a quality transition experience" by perfecting the adCenter to meet marketers' needs.

With paid search results powered by Bing around the corner, marketers will want to get more familiar with the Microsoft adCenter. It will also be interesting to see how the fruition of this search alliance impacts the search market when deciding where to spend ad dollars.

It seems Yahoo and Microsoft still have a long way to go if they hope to catch up to Google. ComScore's July 2010 search rankings indicate that the two search engines together accounted for 32.7 percent of core searches – around half Google's current market share.