in large numbers, slow zombies aint no joke. plus, the slower zombies are far more ruthless than the faster ones. they tear you apart, rip your guts out, peel the skin off your face, and they do all that in front of people. the faster ones probably do the same thing but they must be a bit more camera shy because their movies didnt show them doing shit half as gruesome as the slower ones did. in this old old italian movie ZOMBIE one of the slower ones fell off a boat, into the ocean, and then ate a shark!!