The idea of raked wingtips is associated with something called the Schuemann Planform. From my understanding, the Schuemann Planform is a set of aerodynmic priciples and rules regarding the design of a wing according to some guy named Schuemann. How strictly Boeing conforms to this planform I don't know, but Airbus has used ideas from it as well in the A310/330/340 (all aircraft who also utilize the raked wingtip. Google it, maybe you'll learn something.
"If you're going to crash, make it a fiery one."