Microsoft (NSDQ: MSFT) has bought travel search engine Farecast the company told SeattlePI, after the paper reported a few days ago that the site had been sold to an unknown buyer. Deal terms were not disclosed, though the report pegged the price at somewhere between $75-$100 million.The two are geographically close, as Farecast is based in Seattle, and the site had already been a partner at MSN Travel. In addition to traditional flight search, Farecast has garnered attention for an algorithm that purports to predict future prices of a seat, so that travelers can know when is the best time to buy. The site has raised nearly $21 million over three rounds from investors including Sutter Hill, PAR Capital Management, Pinnacle Venture, Greylock Partners, Madrona Venture Group, and WRF Capital.