Even that reputable source Wikipedia can't adequately explain why people would throw their shoes over power lines.
There are many references - none of them with any authority - that suggest it has something to do with drug dealers marking out or identifying their territory.
If that's the case there must be an awful lot of drug dealers in the area around where I live. This one was taken near the rail bridge at South Brisbane this morning
I hear from another authoritative source - Eddie McGuire - that power companies consider it vandalism and a potential threat to power supply.
The power companies are quite dismissive of the potential drug link. Personally I think there must be something in it.
Certainly if I actually managed to throw a pair of shoes high enough and with enough precision to land over the power lines I think you'd have every right to drug test me. There would have to be some artificial performance enhancer at work.
In addition, given the cost of shoes I think you'd have to be on drugs to think throwing them over power lines was a good idea.