Some analogies - Internet connectivity - Years of stats tell providers how saturated their backbone is in sold plans versus expected bandwidth usage. Airlines overbook seats based on known trends of no shows and cancellations. CLEC's resell less expensive metered lines as unmetered, knowing the odds favor them.

Let's face it - an awful lot of web hosting providers oversell their resources. Successful providers have figured out either how NOT to oversell (and still turn a profit), or oversell with minimum customer churn.