Microsoft stated in the announcement that "Hadoop has emerged as a great platform for analyzing unstructured data or large volumes of data at low cost, which aligns well with Microsofts vision for its Information Platform. It also has a vibrant community of users and developers eager to innovate on this platform. Microsoft is keen to not only contribute to this vibrant community, but also help its adoption in the Enterprise. We expect a preview version on Windows Azure available by end of the calendar year."
Microsoft recently disclosed that it would not be going forward with its proposed alternative distributed Big Data platform that consisterd of a production line of LINQ to HPC. Instead, they will be developing Hadoop distributions for Windows Servers and Azure.