I can say for myself that when I changed my timing belt and I had to take the pulley off, I found at reassembly that there is a special tool used to hold the crank pulley while you tighten the bolt.

My repair manual suggested putting a large screwdriver in the flywheel gears which is hte method I used. I held the screwdriver in place, lying under the car, while my 12 year old son pushed down on a breaker bar. I have to honestly say that I have not had a problem, but I wonder from time to time if that bolt is really up to spec.

I don't know if there are any cases of that part of the crank failing, or the bolt working itself loose... both would surprise me. I think someone didn't tighten it up to spec. Maybe whoever did the timing belt? Hopefully the only damage is the thrown belts and the timing belt gear didnt move.