I was at hostgator and got my site suspended for causing too much load (not over using bandwidth though).
Installing wordpress super cache did solve that issue and reduced the cpu load my site was consuming. However, I dont have a good solution for reducing bandwidth consumption other than trying to optimize your site as much as possible. If the bandwidth does become an issue, you could always setup another hosting account with its own domain, and put some of your static content such as downloadable movies, swf files, etc on each hosting account to spread the load (although your wordpress site and database will always be under 1 account).
Lastly, for one of my sites, I had no choice but to purchase a dedicated server. I bought one from take 2 hosting for $99 a month and have found it to be great so far.
