Positive Message Billboards

Do they have them where you are? Big, white, blank billboards with just a few words printed on them in big black font. "SMILE" or "BE GRATEFUL". I keep wondering when they will add "OBEY". There is one on the road I used to take to work (before road construction season) that said "Smile". I farking HATE when people tell me to smile. I always, ALWAYS flip off the sign when I see it. Apparently I am not the only one to loathe those billboards.