The thickness of the cable is where it's at. With a good set of bolt cutters, I've cut through many a chain (not bike locks, but others), yet it's hard to cut through wire, as it moves around, etc. Any bike is steal-able, but it's all about time. If it takes 10 minutes to cut through a cable, that's a long time for you or someone else to go up to whoever it is and ask what the f*** they're doing.
And as for the second - I was given a bike a couple months ago that I strapped to my rear Wald baskets and carried home, and just Tuesday I was given a Kabuki that I pushed home while biking my fixie Peugeot.