I am a Nevada State Licensed Contractor, I have been a contractor going on 29 years. We are all alarmed at the recent statistic shared by the California Realtors Board. Graffiti can negate your homes property value by up to 20%. If we try to get involved and confront the taggers we run the very high probability of getting shot. Two workers have been killed while removing graffiti and two women in different cities were killed when they just confronted the taggers. (I have attached the News clipping below!) I specialize in deciphering graffiti and identifying the gangs related to the markings. Graffiti is being used to sell products. If you look closely you might see My space names, Websites and even phone numbers. All are being tagged with the intent of selling everything from drugs to AK47's.
I have been working with DOTs, DOE, Chambers of Commerce, and Gang Task Forces trying to help educate our many cities about graffiti and its vast effects. Here in the USA are spending over 40 Billion on graffiti and related issues.