It makes more sense to me that I get interrupted when I am hit, and stop casting. Moving while casting is different.
Also a major factor with attacks canceling a spell, the power of the attack should exceed a limit. Why should an attack that does 1 damage, but blows me 10 feet backwards stop me, I am still standing up on my two feet, the damage inflicted should not have been able to make me go "OW F*beep*"!
