For those of you who don't think smiley face tagging is positively whimsical, be sure to use 311's Graffiti Reporter. You can help erase mischievous displays of graffiti you find in public parks (Golden Gate Park, John McLaren Park, and other playgrounds and park property), on private property (personal residences, homes, office buildings), on public property (bike racks, trans cans, newsracks, mailboxs, public toilets, parking meters, fire hydrants, etc.), or any other location that affects your sacred quality of life (MUNI buses/trains/cable cars, billboards, bus shelters, BART, Caltrains, schools).
To use, simply dial 311 or go here. After providing them with the location where service is needed (address or intersection), nature of the jarring graffiti ("offensive, not offensive"), and what kind of building or object said graffiti is on, DPW will paint over the "public art" on said property and notify other agencies and private property owners of the presence of graffiti, so they can remove it. And then feel your quality of life increase tenfold. Ta-da.