Years ago I was racing an old track bike and the wooden rim on the front disintegrated on me. Fortunately I was young, in good shape & was able to roll out of the way of the pack, so I walked away relatively unscathed. So my answer would be that when they fail, they really fail.
Also I would think they are a little hard to come by. But they are nice looking.
Mary Lanphier
Sick of snow in the Detroit area