[Freakinout]

the petcock could have gotten a leak, or the fuel hoses might have gotta messed up, but I don't know of anything you could have done to cause it to get a leak (aside from wrecking it, but thats quite noticeable). I ride my bike hard and have never had leakage problems.

you may also want to make sure he isn't overfilling the gas tank, it has a overflow hose that comes out below the seat.

if you figure where under the bike its coming from it would be very helpful.