I went through a few of these. At least once the GPU burned up when it failed to go to sleep after disconnecting from my thunderbolt display and putting in my laptop bag for 18h.
I think I went through two MBPr 15" machines before I got one that didn't have the problem. I still think it's possible some software I had was triggering it initially, but once it happened a few times, even a clean install with nothing on it could trigger it. Was very frustrating.