The practice of throwing shoes (or boots) in the air to wrap around a utility line (power, phone, cable, etc) has been described as everything from “angels feet” marking the death of a gang member to “just another prank by drunken students“. There are web-sites dedicated to discussing it, celebrating it, recording it. One person decided that since the shoes tend to hand around for a while, it is a form of graffiti and coined the term ‘shoefiti’.
I offer no opinion as to the origin or symbolism, but living in an urban area, I frequently see them. And being a photographer, I take pictures and I’ve started putting my favourites on greeting cards and apparel at one of my Zazzle shops as well as at one of my CafePress shops.