The answer to this question depends entirely upon what kind of site you have and how much daily traffic you anticipate. It is important to note that sites with an abundance of multimedia content will often consume more bandwidth. This is because more data must be transferred instantaneously to stream videos or music to the visitor's computer.
If you have a site with plenty of streaming content, and you foresee a high amount of daily visitors, then you will want a plan with excessive bandwidth. Hosting plans like VPS, dedicated and even reseller hosting plans are perfect for such sites.
You may also need a lot of bandwidth if you have thousands of daily visitors, and/or plenty of page hits from each visitor. Every page that loads will consume bandwidth because it has to transfer data from the web server to the visitor's computer.