I like to stop by a yard sale from time to time in search of a deal. One of my pet peeves is people that don't take down their yard/garage sale signs when it is over. It bothers me more than it probably should. I once rounded up several signs for a specific sale because they had the address on them. It was easy for me to know just who's lawn to throw them on. Aside from the fact that the old signs start to look trashy after a while, they also have the ability to waist people's time driving around looking for something that no longer exists.
I have recently discovered I have another pet peev. People who list things on line, but can't be bothered to remove the listing, or change the status to sold when it is no longer available.