No one can say definitively what the meaning of sneakers or shoes tossed over power wires is, but in many areas, ours included, it defines where and when drugs can be purchased. I have looked all over the net and many sites state that it is an urban legend that this means nefarious activity;it's children playing, it's kids who are just bored and in some cases that is just what it is. However, a friend of ours who is a recovering addict let us in on the little secret when it was mentioned that shoes were dangling from various power lines in various places in the neighborhood. The shoes are not a permanent fixture in each location, so the fact that it's bored teens or kids does not jibe with where and when the shoes are seen.
Within our community group we have found that when we do "walk arounds" in the neighborhood that the frequency of the shoes appearing drops. We don't ever engage those conducting business that we would rather see stopped, but when the perpetrators of these practices see that there is NOT "no one around" it makes it more diffcult for he/she to conduct business.
So if you see a pair of kicks or shoes hanging from a wire, if they are your size take em, otherwise report their presence to your local law enforcement and document everything.