Yahoo has purchased Flickr -- essentially a web community that shares and tags photos. In Flickr terms a tag is a category attached by a human (probably).
Here are the flickr results for graffiti.
Real humans attach their notion of meaning to photos they upload. Suddenly I have a few tens of thousands of photographers working for me. I'm a photo editor!
Not only that, I have a chance to integrate with grafedia by posting a picture of my own (or your) grafedia, posting it to flickr and tagging it 'graffiti'.
How cool is that?
The possible synergy with google's adsense is interesting -- a photographer has the chance to use adsense (money for google) to sell photos on flickr (money for yahoo) thus making money for the photographer. Will photographer's hijack flickr?