Both the News and the Post have run articles about Denver's growing graffiti problem in recent weeks. As more of us subscribe to the "Broken Windows" theory (even as fewer of us subscribe to the papers themselves), this is a very bad sign indeed. Graffiti can either be a gang-tagging or individual ego-gratification, but in either case, it's a leading indicator of very public trouble.
Neither article bothered to mention Denver's Police graffiti hotline, part of Denver Partners Against Graffiti, where you can call to report graffiti and have it painted over. I've called in the past, and spoken to the cop who interprets the stuff before they obliterate it. In the case of gang members marking their territory, getting a good look at the tags before they're painted over can help track gang movements and ambitions.
(This reminds me of a Victor Borge joke that got him put on the last boat to America.
Q: What's the difference between a Nazi and a dog?
A: A dog lifts his leg to relieve himself.
Gang members seem to have the same, er, problem.)
Here's the number: 720-865-STOP(7867). Use it.