After 4 weeks of having the 3rd replacement rMBP, the same black screen issue has occurred.
It can't be old corrupted software as I didn't restore from my previous replacement, and it would be unlikely to have been hardware as this is machine number 4. Must be some inherent flaw with either the design or the process of updating from Mavericks to Yosemite. I'll be getting on to Apple again soon but I've never had something like this happen ever before.
I think it has rather something to do with your usage or your environment. Millions of people own that computer and many of them have updated to Yosemite without these kind of problems. I also can't recall a story like this being reported on the forums. Is it possible that you stress the laptop somehow, or that its exposed to some stress (dirty power, smoking, heater close nearby, being used in bed where blanket covers the air intake, etc.)?
Or someone in the Apple store is deliberately messing with you. Maybe even a higher power