A Pinarello F12 came in recently with a fracture to the drive side chain stay.
In all honesty, hard angles in frame design aren't really a good thing when it comes to carbon. Load can't distribute evenly around a hard edge, so it tends to concentrate at that point, and do more damage. Hard angles also don't mould as well, so manufacturing faults are much more prevalent. A curved cross-section distributes load much more evenly.