I think that if you live in or have to park in a shady area, definitely find a secure place to lock your bike to. Preventing thieves from riding off is great, but as a friend of mine said, a few guys can put a couple two-by-fours between the spokes and just pick it up and throw it in the back of the truck, then take it wherever they want and have all the time in the world to cut off a disc lock or something.