Yeah, it looks funny. A spray painted sign on a board. But it's much more than that to me. This person is looking out for their fellow man. Something that no one seems to do, or even thinks to do. This person took a step back and thought "how will this affect those around me?". They then went one step further and took an action to warn others of a potential danger. How many other people even think to do that? How many people think with the blinders on, only considering how things are going to affect them? It takes more than just empathy. It is a whole different way of thinking - the ability to see the big picture, take all the variables into account, and consider how they will affect not only oneself in the immediate, but others as well and in the future.
The world needs more people like this.
"Remember, I'm pulling for ya. We're all in this together."