dude they have been able to do back flips on motocross for about 2 or 3 years... Think more to 3 maybe 4 years.
pretty sure it Travis Pastrana tried his first back flip in the 2003 motocross x games. Right at the end of the set he rode up to the jump pulled off a sort of back flip with a mini flair,,, the flair part was by mistake. He didnt land it properly he went a tad too far and landed pulling a manual out of the back flip. but it opened the path. Last year in the 2005 Travis Pastrana was pulling back flips one after another. no footed backflips, no footer with one hand backflip and think he even pulled off a flaired black flip. Was sick... but he made the backflips look easy.
Saw some footage of him doing sick tricks into a foam pit. His going to be doing some sick stuff at this years x games.