One problem I have found with this system is that the wafer thin master pins that are sometimes used, make the lock bind when your key is turned to open the lock. This will make some people use graphite or other lubricants to try and make the lock move more smoothly. The only problem is that over time this causes the lock to bind even more. Sometimes scoring the of the plug.
When I find locks that are labeled "Protecto-keyed" I will take the lock completely apart and re-assemble with only the required "Top and Bottom Pins". This eliminates future problems that might be caused by these pins binding in the lock.
The thing is this is not something that is only done with one lock manufacture, I find locks of Schlage, Kwikset, Yale, Dexter and Ez-set. The lock may or may not be labeled with some kind of recognition, but when pulled apart it is usually a subtle sign of ball bearings or sometimes one or more wafer pins gets caught on the wrong side of the shear line when I pull the plug out. In any case when I see the sign I remove the problem before it is one.
If you are having problems with your locks or see your locks labeled as such, it is a good idea to have preventive maintenance done and have those pins removed.
Have them Re-Keyed by a locksmith that knows about this problem!!
