A far better way, IMHO, for hosting companies to ration bandwidth is, instead of having a monthly limit, do what powweb.com does (or did, at least when I used them a year or two ago) and have DAILY bandwidth limit of, IIRC, 5gb.
If you approach your bandwidth limit, you are sent a warning e-mail, and you can start to take steps to reduce bandwidth usage. Worst case, if you go over your limit, at midnight you're back up and running, as opposed to being down for, in this case, almost a week.
--Mike