a lot of the injuries with kettle bells are from people starting with one thats too heavy and lifting 'with their back' so to speak!
They can cause injury but so can taking the washing out of a washing machine (if you're me)!!!
I think between you both (Neph/attitude) you have both hit the nail on the head! You can get a good workout from any manual laboring replica, and more and more gyms are trying to emulate this in their strength and conditioning training (i know we do) BUT you do need someone there who at least knows the ways in which the body is likely to get needlessly injured if main points are not adhered too, lifting via legs, not over extending etc etc and yeah, this is all simple stuff that people who have done this shit in their lives know about (working in manual labour/studying health & fitness etc) but the amount of people that come into a gym who have literally never done any sort of fitness or s&c fitness before is unreal, and them picking up a 20kg kettlebell, swinging it up and down, backwards and forwards, in a vain effort to impress, whether or not its hurting them = some sort of ridiculous injury for them!!

so to get to the point, most people are actually that stupid (myself included in my early yrs of training) which is why its important to have someone to show you how to do stuff safely! a gym is not a farmers field, and unfortunately these days people sue over paper cuts so good, safe guidance is a must!

ps attitude, the biggest injurys in my experience are from dropping them on your feet ;)