Microsoft is one of the first--and certainly the largest of--customers of Wolfram Alpha's commercial API (our Wolfram Alpha API profile). For math and nutritional searches, Microsoft's Bing now uses Wolfram results.
From the Bing announcement:
This notion of creating and presenting computational knowledge in search results is one of the more exciting things going on in search (and beyond) today, and the team at Bing is incredibly fired up to bring some of this amazing work to our customers.
When the Wolfram Alpha API was released in October, we saw the promise of connecting to its data and algorithms. The connection with Bing is appropriate, given how the search engine has framed itself as a "decision engine."
Epicenter notes the integration is part of a larger trend:
Microsoft's decision to try out some of Wolfram|Alpha's answers is yet another step in an industry-wide march towards returning more than just links as the answer to most search query. Search engines now routinely blend in maps, music, videos and reviews, in order to give better results to user queries.
In addition to being a coup for the young Wolfram service, this is healthy news for anyone charging for an API. Microsoft has validated not just Wolfram, but the idea of an API as a revenue stream.