Yes, there's that too, but I might actually give the point to antithesis here (as much as that pains me) - to his point, has anyone ever been prosecuted for not registering?
I think that you're more likely to lose a job for not registering, I've seen the question on job applications "Have you registered with selective service (if required)?" Now, whether the companies actually follow up on that and verify your answer is another question, but they can tell the government that they are asking the question.
Also, it's pretty much a moot point since we're all registered if we're over 18 and have a drivers license. The only people that aren't registered are those that don't get a drivers license AND go out of their way to not register.