Ok, check this out. A couple of civic minded flickr members have started a group that's intended to serve as an "unofficial companion" to 311 reporting. Anything that one reports to 311, such as potholes, cracked sidewalks, graffiti, illegal advertising, is pictured there. In fact, one of the rules of the group is that you call 311 to report the problem you've photographed.
I was wondering if they've sent the link to anyone in city government so I posted the question in the discussion area of the group. It's a great idea, go check out this group.