Bolt Failure

When I give anchor clinics at Gear Shops and Climbing Gyms, I always get the very logical question:

• If bolts are so unreliable, why aren't bolts failing left and right?

A single crag in Santa Barbara has actually had two different bolts pull out during lead falls (most recently in Summer 2007). Both cases involved 5-piece Rawls, which are considered better than most other bolts in softer rocks.

And then this in Australia: bolt failure in the Blue Mountains