Apple has acquired the social media analytics startup Topsy.

The acquisition was first reported by The Wall Street Journal, which says the deal was worth more than $200 million.

Topsy is one of the few services that has access to Twitter’s data firehose. It offers users a way to analyze tweets, gather sentiment and measure the reach of a campaign, hashtag or message. In September, the company rolled out the ability to search Twitter’s entire archive.

Topsy is an interesting acquisition for Apple because unlike its past purchases of startups, such as HopStop and Locationary, there isn’t a clear product application.

The same could be said for Apple’s acquisition last month of PrimeSense, the company responsible for the original 3D sensor in the first Xbox Kinect. But at least with PrimeSense, it stands to reason that Apple would be interested in implementing those sensors in future products.

With Topsy, the purpose is less clear. The Journal posits that it could be useful for iTunes Radio — a product that already has direct integration with Twitter Music — or its flailing iAd product. Still, the purpose of acquiring an analytics firm that is so focused on one specific social network is, in a word, odd.

An Apple spokesperson has not responded to our request for comment but told the Journal that “Apple buys smaller technology companies from time to time, and we generally do not discuss our purpose or plans.” We have reached out to Topsy for further comment.

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