Well, there are far more vague warnings than there are actual failure reports.
My guess is that if you wreck hard enough for the extender to matter, it's a toss-up what else would have failed first if the extender wasn't there.
I've used a quill type for a couple of years w/o issue. I've used the BBB one for a couple of weeks. Worked perfectly fine for the time, but I didn't fancy the kludgy look. I'd think I'd prefer it to the Satori/Zoom type clamp though.