Personal pet peeve undefined acronyms, "CPR": Central Person Register. For those who didn't know, like me, and had to look it up.

I always find the use of acronyms a lack of education and manner. A way for the uneducated to try to sound sophisticated.

When I get an internal mail with multitude of acronyms I know that the people that wrote it does not care if anyone is going to read/understand it or not. It goes directly into the trash.