Quality Bandwidth is one of the top cost components of webhosting. Most hosts who offers unlimited bandwidth actually do limit to the bandwidth in their terms of service agreement.

Tehcnically there is no such thing as unlimited bandwidth. Normally if you get famous and your sites grow, such hosts will find a way to shut your website down.

Also, there is a limit in terms of server capacity as to what kind of bandwidth it can push. Truth is, there is no unlimited bandwidth. Read the fine print.