Kind of ironic, but I was due for my glock armorer recert, so I asked the instructor about it last week. He said that the .40's are really hard on the guns pins and recoil springs. (I only shoot factory WWB and AE through mine). He also said that shooting with a non glock flashlight is harder on them too.
Mine is a 3 pin glock (2003). The instructor said most of the broken pins are from them not being correctly seated. He said to use a rear corner of the glock armorer tool as a guide to properly seat the locking block pin and the trigger pin.
Both times, it's broken the G22 continued to shoot just fine, the right side of the pin just falls out since it's not under spring tension.