Three Dimensional Graffiti

People often leave their traces in wet cement or concrete. This type of graffiti often commemorates the mutual commitment of a couple, or simply records a person's presence at a particular moment. Often this type of graffiti is dated and is left untouched for decades, offering a look into local historical minutiae.
Commercialization and entrance into mainstream pop culture
With the popularity and legitimization of graffiti has come a level of commercialization. In 2001, computer giant IBM launched an advertising campaign in Chicago and San Francisco which involved people spray painting on sidewalks a peace symbol, a heart, and a penguin (Linux mascot), to represent "Peace, Love, and Linux." However due to illegalities some of the "street artists" were arrested and charged with vandalism, and IBM was fined more than US$120,000 for punitive and clean-up costs.