I currently carry a cable lock for an emergency stop for food while I am out. I refuse to be out of line of site of my bicycle for very long. When I lived in Florida I used a Kryptonite heavy chain with the little U lock on my mtb. I went shopping one evening and locked it to the WalMart bicycle rack thing. I walked out of the store and when I looked out at the bicycle rack my chain and lock were on the ground next to the rack. Another person couldn't help but notice the battery powered grinder he had used and pointed the thief out to me. He was almost to his pickup truck. I caught up to him as he was placing my bicycle in his pickup truck. Without a word I rammed him with the shopping cart. I have considered electrifying the whole setup but this could be problematic. I only want to hurt, disfigure, eviscerate, draw and quarter or put through the wood chipper thieves. Not everyone else.