So, I first discovered this after I blew up the internals of my right/rear shifter, and was forced (until I adjusted the high-stop screw to force me over to my 12t cog) to ride around in 50-11 on my 20sp/compact drivetrain. Under sufficient power (read: I'm 180lbs, and singlespeeding in 50-11 required significant restraint to avoid problems) I can throw the chain off the outside of the big ring. More recently I've found that I can torque hard enough at speed to do this, too.
I'm running a -reasonably-, but not insanely, stiff ~3.5lb (@61cm) lugged unidirectional carbon frame, with Rival cranks+ring/cassette, and had this problem with both the original PC-1070 chain and a KMC DX10SC.
I have my own thoughts on things that are contributing to this, but I'd like some clean-slate input first.