Agree with Aaron. Huge bandwidth are not really needed unless people are on video and music streaming. However bandwidth must not be made as an issue. It is better to have as much bandwidth as possible as it's only meant to give accessibility.
http://www.findmyhosting.com/truthunlimited.htm
So Why Do Unlimited Plans Exist?
Most websites only consume a very small amount of bandwidth and disk space. Web hosting companies that provide unlimited anything as a plan feature are banking on the fact that you won't use very much. Unlimited is a marketing trick to get your business.
It's the consumer problem who wants to get tricked. We don't lose anything if they consume only small amount of bandwidth. However if they are really consuming a lot.. it is our problem as we are playing tricks on them. Debating into bandwidth again? hehe
