I don't know when it was exactly, but sometime in the past couple of years, I stopped looking at graffiti as an eye sore or pure rebellious vandalism and started looking at it as a simple way to claim a place as one's own. I think of it like a dog peeing on a fire hydrant or a hunter blazing a tree. This is the little window that opened up after I made that transition of observation.
This is a New Yorker piece about two different guys that are walking/have walked every street in NYC: https://www.newyorker.com/culture/culture-desk/the-city-so-nice-they-walked-it-twice
SF Gate piece written by the walker, Tom Graham of his 7-year project: http://www.sfgate.com/entertainment/article/Tom-Graham-walks-every-street-in-San-Francisco-3182272.php
NYT piece on Matt Greene on his walk of every street in NYC: https://nyti.ms/2tzPqGu
New Yorker piece: https://www.newyorker.com/books/page-turner/a-walker-in-the-city