Think about it this way - when someone's looking for an employee, they chose the Harvard graduate over the random kid from a no-name school. Schools of higher rankings have children with higher intelligence and children with higher intelligence earn more money in the real world. They donate money to the school so the school can spend it to facilitate the learning of children, and the rich alumni can introduce students to employers, giving them a better chance of getting a job.
People who think rankings don't matter usually couldn't get into those prestigious schools, and make themselves feel better by saying that it doesn't matter.
Yes, college rankings are important depending on your field of study. If the prospective employer is a top company that wants only the best of the best employees, than your rankings may score some points. Especially if you lack years of job experience, your grades may be an indication of performance. Overall, I think rankings are more of a self check, to compare your efforts to others.
With the tough economic times, it's hard to get a job these days. It's even hard to get a job if you're just coming out of college. Your fancy degree from your fancy school won't matter if you don't have the prior work experience in your field and the connections that are afforded to you if you attend a less prestigious college.