What causes a harmonic balancer to come apart?

Friend recently purchased a 97 WS6 M6 w/98,000 miles on it. When the car was in the shop for some other stuff the shop noticed the harmonic balancer was starting to come apart.

The only other car I've seen with a balancer failure like this had been beat on with lots of high rpm abuse.

Does that have any effect on the balancer?

Thanks.

 

I would assume that the rubber between the two parts just deteriorates over time. Mine is starting to show signs of needing replacement.

 

improper installation/removal or age are really the only things that will make them come apart.

 

using a old style 3 prong pulley puller to remove them can cause them to fail.