I’m fortunate to have a hosting service that provides bandwidth on the cheap. For $20 per month, I get 100 Gigabytes of bandwidth. In one sense, it is good that I’ve never come anywhere near that limit. On the other hand, why put the effort into a website if no one is looking at it? As your site gets bigger (or gets the love from Fark, Digg, Reddit, etc) you face a choice: pay for more bandwidth or reduce the bandwidth usage of your site?
At first, reducing your bandwidth might be as easy as resizing a few images, but that only gets you so far. So what then? Make use of free bandwidth, of course! Have a few charts on your website? Use the Google Chart service. Have a large number of pictures? Host them on places like Picasa, Flickr, or Photobucket. All of a sudden, you’ve got a much bigger cushion, for not a penny more. As your site gets more popular (and hopefully starts bringing in some revenue), you can pony up the cash for more bandwidth, but why not save it while you can?