What I found interesting in both cases was teh belt flew off in one piece. it also made the ac & p/s belt fly off in the process...In the miata I was able to simply reinstall the belts and refill the radiator on the side of the highway and continue to the auto-x I was travel to. I ran 8 runs and drove home to discover that I had a small hole in my radiator tank.

 

Mine definitely broke. The flailing belt knocked the overflow line off as the steam was the instant the belt broke.