and 30 fps for NTSC

Frame rates were designated so that things looked like movement, not a series of images one after the other (which of course they are) not anything to do with speed.

Lowerframe rates save on bandwidth when it comes to making the movie file (such as the 15 fps options in flash) so its all down to compression, it probably employs some sort of tweening of bluring between the frames to make it look better so you can get away with it.