My collection of rubberstamped money. A couple of years ago I became aware that ordinary people have been using currency to spread ideas. I had received a few I GREW HEMP bills, but was awhile before it dawned on me that people were actually using cash as a communication channel.
Some bills advertise political opinions.
Others share highly personal messages, I suppose many of which are in-jokes. And some are probably just artistic creations. First of all, money is inherently valuable. So no matter how obnoxious or antithetical the statement on the bill may be, you're still going to spend it. Unlike a poster or flyer, which you would simply discard.