One of the comments in Engadget offers an interesting idea:

"
You guys are all WRONG. Microsoft and HTC are pals. Microsoft just helped HTC big time here...

“Microsoft Corp. and HTC Corp. have signed a patent agreement that provides broad coverage under Microsoft’s patent portfolio for HTC’s mobile phones running the Android mobile platform” (Emphasis mine)

So yes, this seems to be Microsoft lending its (undoubtedly massive) arsenal of patents to help HTC and Google combat Apple (though, naturally, the rationale behind the deal — and Apple — are never named). It’s hard to imagine what else this could possibly be about [more below]. It’s also hard to figure out why Microsoft sent this release out at 11:30 at night."

http://www.engadget.com/2010/04/28/m...ents/27474201/

So, let's imagine this scenario: When Apple takes HTC to the court, HTC could invoke Microsoft's patent licensing coverage as a defense...