It's taggers vs. artists in San Francisco's graffiti war

Artist Carlos Daniel Perez-Boza works on an authorized mural in the Mission District.

Mats Stromberg's "Giant Selfie" mural has been all but obliterated by tags.

The brick walls of San Francisco's Chinatown are an ideal surface for muralists.

Taggers spray-paint initials, names, words, acronyms and other lettering across virtually any surface they choose.