Yesterday, I was asked to rekey a store front lock for a business after an employee "disappeared" with keys to their business. Rekeying after a person leaves your employment, whether it is under good or bad terms, is always a good idea. Rekeying has a relatively low cost compared to the possible risks associated with unauthorized people having keys to your business.
Now, to the main point I want to make today: If you look at the picture above showing the "key cylinder" (mortise cylinder), you'll see how badly the previous locksmith(s) had damaged the cylinder threads. When I proceeded to remove the cylinder, I only had to rotate the cylinder about 1/4 turn before it just fell out of the door (it should take multiple turns before a cylinder comes out). I was in complete disbelief that a licensed locksmith had damaged the threads so badly or chose to install a previously damaged cylinder without replacing it. Of course, it is possible that the previous locksmith company tried to sell a new cylinder to this business at an elevated cost and the customer declined. However, there is a difference between "up-selling" something the customer doesn't necessarily need and leaving the job "jerry-rigged" with a severe security risk. After I properly explained the issue, this customer wanted the cylinder replaced. Even then, we didn't take an advantage of this customer and replaced the part at our cost which was minimal (the part cost less than the sales tax on this job). I simply don't understand how any conscientious locksmith could sleep at night after leaving a cylinder secured only by the set-screw (and not by threads that are really supposed to hold it in place). I am not going to name the previous locksmith company, but they are one of the oldest and well known locksmiths serving San Diego. The previous key even had their name "proudly" printed on it.
PS. We also carry a cylinder "tap and die" set in our van and we could have fixed the threads rather than replaced the cylinder. However, in this case the threads were quite severely damaged and the cost of this particular cylinder was low, so a new cylinder made the most sense.