noglider 

I've been riding a bike for a long time, and I've had only one incident where a collision damaged a wheel or frame, and in my case, it damaged both. That was in 1982. I don't have statistics, but I think a collision-caused failure occurs less often than once every five years.

I don't lock my bike in public that often, so I can't speak much of damage done at a bike rack. I've had plenty of bikes stolen, though, so that is a very serious risk. And lots of people leave their bikes locked up in my neighborhood 24 hours a day. They get cannibalized a lot.