Actually....I have, a couple
One cracked through the cast, seen one break a pinion out, several spit teeth through the cover, a couple even trough the cast, yep, tube spins, lots of bearing problems, and some other random problems.
BUT, I could say that about almost any axle....seen a lot of broken axles over the years....some were VERY impressive!!
Seen the least problems with 9" and 44 rears, considering how many are out there, I have seen very few problems comparatively.
The big FF don't have a lot of problems, except I have seen lots of burned up spindles because people never service their wheel bearings.
Favorite break ever was a full size late 70's F250 that we had built several axles for. Finally we built him a "bulletproof" 14 bolt (10.5) with Dana 80 spindles/bearings/hubs. The guy was running a hopped up BB Ford. Yep he broke that too!! Double Wammy on GS. He had his foot in it, bounced off both ledges at the same time, truck hopped in the air, 3ft or so, gravity pulling him down hill, tires still spinning forward, SNAP!!!!!!!!!!!!!!!!
Loadest break ever too. Both shafts!!