Does this effect dual booting OS X? I doubt the side-effect of blocking Linux boots was anything but a coincidence. But could Microsoft be fearful of Hackintoshes becoming more popular and a increase of OS X running on non-Apple hardware?
I doubt it. Whilst I don't mean to belittle the hard work that goes into the hackintosh projects out there, we're talking about a tiny, tiny group of people that probably have an imperceptible impact on MSFT's bottom line.
I'd be more worried about Apple waking up one day and shipping an update that breaks everything.