Tolerance of water pump play?

I seen my friend loose a rad, shroud, and a hood from a pump shaft breaking off back in the 70's, blade went through the hood.
There was a Montgomery Wards Service Center down the road from my house back then and a Mechanic lost his arm to a fan blade that came off while he was leaning over the engine revving it up. From that day on I have never leaned over a fan on a running engine.