_95th%ile is not a robust mechanism for billing_ It neither addresses variance nor average use effectively and can be gamed quite easily. It's some kind of best fit system for billing buyers with "normal behaviour". Where in maths class did they ever say that scraping off the highest n percent of a data set in isolation, gives a good indication of anything? Don't you need to look at the mean and 90th percentile together to fairly evaulate distribution. I think the reason it's so popular currently is that it's easy to describe (hence sell) and fits normal use reasonably well, so from a "normal buyer's" perspective is OK. Just as long as everyone is honest. In a thirty day billing period 95th%ile gives you one and a half days of *free bandwidth*. 90th%ile gives you three days of *free bandwidth*.
From the seller's perspective, once this starts getting gamed a little more I can't see it having much of a shelf life, and more sophisticated billing will surface, similar to the power industry Sean sites.
I'm quite surprised we're not there already.. has anyone started venturing down this route yet? (other than flat rate) toby