What about Bing? Microsoft didn't get into social because that is entirely outside their market. The limit of it seemed to be something like msn messenger, which had business use cases as much as social ones.
I mean, its not like MS didn't try the search thing, but search is something Google will own until they fuck it up, not from anyone entering to compete with them, because free & good enough are hard to break. Albeit, Google has been doing a good job fucking up their search in the last several years.