The Ghisallo was Litespeed's lightest frame and was as light or lighter than most carbon frames. I believe Litespeed advertised it as less than 800 grams. To get it that light, they had to sacrifice somewhere and the result was a quite flexy frame, particularly in the larger sizes.

A smooth, high cadence pedal stroke will overcome (or actually prevent) the flex but apparently your buddy isn't in that catagory. As BCRider notes, he isn't actually losing any energy from the flex so other than appearances, it isn't a real problem.