Common Courtesy

I hope you can read this, the camera in my phone isn't that great. Basically somebody in my building is very unhappy that some other people are hogging some carts. I will say this isn't completely unfounded since I didn't even know there were community carts to be used since I had never seen one.

This just got me wondering if you have to harp on people to get them to do something is it really "common courtesy"? Its obviously not that common or we wouldn't have to teach people about it. I also found this amusing since it went up while the apartment manager is away on vacation. So I guess somebody was lacking their normal outlet for this kind of complaint and decided to take it into their own hands.