I've had several bows fail on me over the years (mostly selfbows, but some laminated bows), and I've heard of lots more. I can only think of two that failed with a FF string on them. Both were old bows, both had skinny FF strings with no padding in the loops, and both had the tips sawed off by the string.
Like someone else said already--if a bow fails and has a FF string on it, the string always gets the blame. If it has a dacron string on it, then blame something else.
I only know of a few "old school" bowyers that won't warranty a bow for FF, and as best I can tell it's not based on results--they just feel like it's a risk, and they aren't willing to take it.
Chad