WHAT?!
i'll take my chances.
reasons you're right:
1. a $100 dollar beater bike, locked up, and stolen no more than 6 times a year and your argument makes sense.

reasons you're wrong:
1. you make the assumption that a bike will only be stolen "once in a while" with a quicker locking method (the truth is that, given similar circumstances, it will be stolen more often than if you were to use the OP's method)

2. most of us talking about locks have decent to nice bikes. the amount of money you'd need to be making for your argument to make sense flies in the face of what most people who need to lock up their bikes, lets say, twice a day make (10 minutes of total lockup time in a day, at $15 an hour and a 5 day work work week, you'd need to work about a year to lose the amount time equivilant to a $650 bike....and thats assuming you'd need to replace your bike being only stolen once in a year. if you factor in multiple bikes being stolen from you in a year, the cost/benefit is blown out completely.)

3. this is classic use of "the nirvana fallacy" argument. no, not the band....

"The Nirvana Fallacy is when you dismiss anything in the real world because you compare it to an unrealistic, perfect alternative, by which it pales in comparison. It wouldn't be a problem, except it keeps us from getting anything done.
For instance, procrastination can happen for a lot of reasons--you drank too much the night before, or you're feeling uninspired, or it's your first time doing gay porn and you're having second thoughts--but one of the most common reasons we procrastinate is fear that the end result won't live up to the "perfect" idea in our heads. Think about the writer friend of yours who has never actually written anything, because they're "waiting for the right idea" for a book to come along.

This is why people wind up living in their parents' basement--waiting for the perfect job, the perfect girl, the perfect friendship--before committing to anything.

If you're not full of that kind of self-doubt, don't worry, there are plenty of *******s willing to supply it for you. Any incremental improvement on someone else's part is mocked as some kind of deluded hypocrisy, because anything short of perfect is not worth doing, so you might as well do nothing, like them. "Ha! You're drinking a Diet Coke with your hamburger? Like that's really going to make a difference!"

Politicians use this to attack any idea they don't like. "Sure, your plan is helping millions of families in poverty. But I found examples of people abusing it! So we might as well scrap the whole system!"

Or, you'll hear radical political types on the Internet say, "I'm not voting for any of those guys! They're no better than Bush! They're all corrupt agents of the NWO! I'm staying home until you can show me a perfect, incorruptible, intelligent politician who believes the exact same things I do!"