First, I would assume services like Netflix are the largest consumers of bandwidth these days, and I know my wife generally watches more overall than I do. Unless you are specifically running some kind of server from home, or torrenting, I doubt most 'geeks' compete with video streaming on a usage basis.
Secondly, the problem isn't with 'usage-based billing' in general. The problem is that this isn't 'usage-based', because the only thing that has changed from the previous billing is a over-priced fee tacked on for people who go over the cap. True usage-based billing would allow for people to actually save money when they used little bandwidth a month, but this doesn't allow for that.
Yes, I could live with a flat per-GB charge. The caps and "overage" penalties are what is annoying. Why do companies set their customers up to feel like they are doing something "wrong" by using more of their services?
WAY back when cell phones were first getting popular I got one through my employer. It was a personal phone, but they allowed employees to get personal phones through their business plan. I paid a very modest monthly flat fee and then $0.10/minute for usage. No caps. $0.10/minute for voice sounds absurd today but then it was quite reasonable and the costs were completely predictable.
Secondly, the problem isn't with 'usage-based billing' in general. The problem is that this isn't 'usage-based', because the only thing that has changed from the previous billing is a over-priced fee tacked on for people who go over the cap. True usage-based billing would allow for people to actually save money when they used little bandwidth a month, but this doesn't allow for that.