For future reference (or, things I learned my first time taggin'):

It takes longer that you'd think to stitch things to objects! It took me almost two hours to install my four small pieces (photos below). Oh, and a note on planning: think about how you are going to be installing a piece when you are binding off. Sometimes you'll want your long yarn tails to end up on the same edge of your work, and sometimes you'll want them to be on the diagonal, depending on the application.
It's exciting! People seem very supportive. A guy from Keep Indianapolis Beautiful wandered by and said, "Hey, I like your door handle!" The whimsical nature of knit graffiti makes the artist and other people smile. They can't help it.

Finally, whatever you do - don't get yourself involved with a knit graffiti crew; their stuff might make yours look like crap in comparison! I'm serious; I was literally flabbergasted when I saw what some of the other Yarnburners had done; it was immense, and detailed, and beautiful. I was completely unprepared for the quirky, random, thoughtful, colorful spectacle of it all!