As alanbikehouston eluded, Kryptonite rates their locks based on the degree of crime where you will be locking your bike. I live in a low-crime area, and have only the Kryptonite 7 ft. cable. I'm pretty sure bolt cutters would slice right through it, yet I do not want to carry around an extra 4-5 lbs of lock in my backpack.

Has anyone heard of rigging a bike with an audible alarm, like cars have? Granted, it would be much easier to disable, but if they didn't know it was coming...

Great project for a young engineer.