I wonder how many times some sort of priority has been accidentally turned on over the years by friends and customers I dealt with?
There was an old guy who kept turning it on, over and over again and it seemed like he was unable to ever learn how to do anything but push manual, scan and the up and down arrows on his Pro-43's. I'm guessing why he turned it on so often was it was right below the scan button. Another guy used to call me all the time, he turned on Close Call a lot and couldn't figure out what was going on.
I always avoided using it on my own radios, it annoyed me no end and seemed to kick in exactly when I was listening to something good. Once I had enough radios, I usually just put one of them on the channel I really cared about, and let the others I had on scan away.