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According to the Service Manager at my large Chevy dealership--he has been there 18 years--they have NEVER had any kind of "catastrophic" failure of an HB. He told me they do replace them for people, and they have had them get bad enough that the belt flies off, but never what you are talking about.
I am not disputing the possibility of what you say. In reality, nobody has posted that as actually happened to them, save for the one or two highly-modified vehicles I mentioned. Few vette owners outside of this forum know what the HB is.
I'm not sure what your idea of "catastrophic" failure is, but here's a guy with a failed balancer. It worked it's way back and caused a leak in the timing cover.
There are other post on this forum that show balancers that have walked forward and chewed into the steering rack too. Most of us replace them before that kind of thing happens.