Graffiti Cam detects graffiti-related motion, snaps pictures and e-mails them to police. It sends text messages to taggers to their cell phones that say, Hey, get down here. It collects TV-quality video on a tamper-resistant, encrypted memory card. It arrives at a time when public surveillance has gained tacit acceptance and when graffiti has become a $12 billion migraine for cities and towns. New taggers arrive to take the place of busted taggers, and they find new walls to deface.”]