Once upon a time, in 2001 or 2002, streetart stickers were a perfect for of personal presentation in public space. They were not illegal and rough punished, like spraying graffiti. So, if you went through a painful breakin-up with your partner (first stickers - Recycle), or if you wanted to give world a possibility to share your language discovery (second set of stickers), you just needed to print your message in your home printer and the second day everybody knew it… (also the people who don't use the internet)