We have a unique opportunity: We own a very large number of lenses and cameras subjected to rather harsh conditions. Basically, we have a laboratory set up to stress test photography equipment and we share those results with you.
Our numbers reflect heavy and hard use. Your personal equipment shouldnt fail nearly as often; it isnt subjected to rental conditions. But this does provide some comparison about how fragile various pieces of equipment are.
Its not completely scientific, but with data on over 12,000 copies resulting in over 2,000 repairs its a bit more useful than posts on a forum going back and forth between mines great and mine sucked.
This list is not a comment about how good a lens is. Its simply data about how often it breaks under harsh conditions. Some of my favorite lenses and cameras are rather fragile.
See:
http://www.lensrentals.com/blog/2013/08/lensrentals-repair-data-2012-2013