My father, son and I have a total of 65+ years working around high voltage lines and seen a few accidents. They are not nice!
People stealing cable will eventually make a mistake and either get caught or have this happen:
http://www.thesun.co.uk/sol/homepage/news/3624905/22k-volts-agony-of-copper-wire-thief-James-Sorby.html
This guy at least lived!
The odd/funny thing about that story is that a 22KV wire is very thin and there is very little copper in it.