If Shaq DOESN'T flop, he's never going to get a charge call on anyone because there isn't anyone in the league who can knock him over!
I think there's a difference between being in position, getting hit, and letting your body fall (just showing the [dang] blind refs that YES, there was a foul!) versus falling down without getting hit. If the offensive player runs into you, and you're in position, the refs ought to call the charge regardless of whether the defender falls down or not. If you start calling charges right, 95% of the "flopping" that exists in the league will cease (the 5% representing Ginoboli).