On 50lb bicycles and the lockability thereof

Mike Estee responds to the cyclist's old saw: "All bikes weigh fifty pounds. A thirty pound bike requires a twenty pound lock. A forty pound bike requires a ten pound lock, and a fifty pound bike doesn’t need a lock, because really, who wants a fifty pound bike?"
What is the utility of a fifty pound bike? Would anyone ever ride it? What if we took the idea of building the fastest and lightest bike, and flipped it on its head. What if we designed for more weight instead of less? How heavy would a bike need to be to not require a lock? How would this change our social interaction with the humble bicycle?
And MAKE:'s Michael Colombo takes the question seriously: "Short of mechanically hoisting your bike up a lamppost, what else could be done? Are all bikes really fifty pounds? In most large American cities a burly U-Lock and/or chain is essential. The Kryptonite New York U-Lock weighs in at 4.5 pounds, and the Kryptonite New York Noose chain is a hefty 6.8 pounds. This doesn’t quite live up to the fifty pound joke, but it can drastically increase the weight of your ride. Most urban cyclists keep both a chain and a U-Lock for versatility’s sake, since they can never be sure what they’ll be locking to. Let’s hear it in the comments. If you had an extra twelve pounds to make your bike theft-proof, how would you do it?"

The resulting discussion is pretty interesting.

Bike Theft: Thinking Outside of the Lock

(Image: Never enough, a Creative Commons Attribution (2.0) image from rednuht's photostream)