I agree this is a major motivation for most of the people arguing against it. It is certainly mine. I switched to a business plan just to get away from caps.

At the same time, I do think they're a bad idea for everyone. If we had usage-based billing ten years ago, I don't think there would be a YouTube or a Netflix. Electronic distribution of games would probably not exist. Major image sharing sites like imgur would not be nearly as popular. Webapps would be less common. People would be much more likely to delay software updates or forgo them altogether.

I think that usage-based billing does represent a major impediment to the continued advancement of the Internet. This is certainly a major blow to any future where cloud-based backups or video sharing are more common or see new applications.