In a move reported to be worth over $200 million, Apple purchased Topsy, the Twitter analytics engine that is one of the few services to offer unfettered access to Twitter’s proprietary data. It offers a concise way to analyze tweets, measure reach, and gather sentiment about a hashtag, message, or campaign more broadly; you can even search Twitter’s entire archive through the service. Why Apple purchased the startup, though, is a bit of a mystery. They don’t, at present, have any stake deep Twitter integration per se, but it could be looking to use Topsy to start metrics collection for iTunes Radio.