Graffiti is like the broken window theory of low level crime - if you ignore it, then vandals will just break more windows. Or in this case, spray more tags.

IMO, a better solution is to apply a graffiti-abatement fee on every can of spray paint and use the proceeds to 1) eradicate graffiti where it occurs: buildings, structures like bridges, rolling stock, etc., and 2) to buy survelliance cameras to catch the miscreants.

The fees can also be used to reimburse private property owners, railroads and other private organizations impacted by graffiti.

Every six months, incease the graffiti-abatement fee until these artists wake up to the fact that it costs too much to leave their tags on every building, bridge and railcar, and their 'art' just gets covered up as fast as they can paint.

They are just like little yipping dogs that lift their legs on fire hydrants to inform other dogs they have been around.

My $0.02