The difference is that most users will still choose easily-guessable questions and answers. You and I may not, but we're exceptional people. ;)I really don't give a rat's ass if anyone else chooses "What color is the sky?" with a response of "blue" to that question. If you let them choose the question and provide the answer, and they do something as downright stupid as that, why should I give a flying fuck? Why should Scott give a flying fuck, either?
I know plenty of people, both friends and cow-orkers, who choose things like their child's name for their password. I'd be willing to bet that at least some people here are guilty of same. Hell, even I have been known to reuse passwords from one website to the next. Every person is responsible for their own account's security under this method. That's the point.