I like VegasDude's posts here...I tried to post my response last night, but the server was down.
Big thumbs up on the hump. It is part of the 'Busa's aerodynamics. Every curve and hump on that machine has a purpose, that's the beauty of it.
The hump smooths the flow of the air coming off the rider's back, and reduces drag-creating turbulence behind the bike. The kicked-up tail on bikes like the Honda Blackbird are like the tailfins on a late-50's Cadillac; all style, no function, no sense.
The hump contributes to that huge top-end, and a smidge to gas mileage (although not if you are taking advantage of that top-end). Every curve on the Hayabusa has a purpose, including the hump. It's a beautiful thing.