Leslie Scrivener writes in the Star about the problem of rampant bike theft, and the proper way to protect your bike, including painting it pink, using two expensive and heavy locks, or riding a junker. A commenter pointed out (what appears to be a cliche but new to me):

"All bicycles weigh fifty pounds. A thirty-pound bicycle needs a twenty-pound lock. A forty-pound bicycle needs a ten-pound lock. A fifty-pound bicycle doesn't need a lock at all."

TreeHugger on how to prevent bike theft:
How to Prevent Bike Theft