This is the kind of blog I love to find, and the raison d’etre of the medium as far as I am concerned.
It’s called “Shoefiti” and dedicated to documenting — both in words from the collective community and on google maps in a great mash-up — the urban phenomenon of shoes dangling over powerlines and telephone wires.
NB: I stumbled on this site after doing a Google search on “meaning of tennis shoes hanging on telephone wires.” It was result #1. Yeah, Google!
Of course, no definitive answer is provided (maybe, there isn’t just one?) but some fun urban legends recounted. Check it out.