Originally Posted by
PlanoFuji
Bicycles are simple machines; however, they are still machines and require routine maintenance. Parts that wear, such as rims, require regular inspection for this very reason. Twenty three years on the same rims... I am certain that they have been showing dangerous wear for some time.
It's hard to tell for certain from a single picture, but it appears that the wear indicator line on the OP's rim was worn smooth in some places, indicating that the rim was worn out and needed to be replaced. If so, then the incident was completely predictable and avoidable.