Why Won't Microsoft Join Existing Standards Efforts? 

Microsoft has stated on numerous occasions that they believe in and support open standards. But from my experience, they do this not by joining existing open standards efforts, but instead by creating entirely new, parallel (and arguably redundant) 'open standards' efforts around their own technologies. And often it seems these new standards efforts are around new, untested, and immature technologies that began life as proprietary to Microsoft--introduced into the standards process when a pre-existing open standards effort already exists, and exists around proven and shipping technologies which were developed in the open with lots of input from a variety of expert stakeholders.

Korn, Peter. Sun Microsystems (2005). Articles>Word Processing>Standards>Microsoft Word