As far as conspiracies go, this one is pretty far 'out there'. Movie director Michael Bay (Transformers) an outspoken supporter of the BlueRay format, recently responded to a comment about Paramounts decision to make Transformers available only to HD-DVD, leaving out BlueRay.

According to Bay:

"Microsoft wants both formats to fail so they can be heroes and make the world move to digital downloads."

Bay says Microsoft has been financially backing HD-DVD over BlueRay to create confusion in the market, as BlueRay is suggested to be the superior format. In short, Bay says Microsoft are backing a known loser to prolong the format wars, buying them more time for them to perfect their own digital distribution system.

It does sound like a bad movie plot, but Microsoft are well know for their FUD complains. If Bay is correct, it's pure genius on Microsofts part.