Frank is a person that writes false reviews about topics he has no idea about. Instead of spreading rumors, he spreads false information. Fuck Frank is just a way to stop the spreading of lies by other Franks.
To elude detection from unwanted solicitors or family when they knock on your door. Pretending to not be home. It doesn't matter if they know you are home.
There was a knock at the door this morning and when I peeked through the blinds I saw that it was the Jo Ho's again so I Ann Franked them. (meanwhile they saw the blinds move)