re: Annoying things people do but they are unaware of them.

Cell phone rudeness:

Blaring any sound (call, game, etc.) from a cell phone in public.

Placing a customer in a position where the customer has to compete with the employee or clerk's cell phone.

Placing an employee or clerk in a position where the employee or clerk has to compete with the customer's cell phone.

Taking a video with a cell phone instead of helping someone who needs help.

With uncommon exceptions, answering a cell phone during any type of business meeting.

I'm sure I'm missing quite a few more.