That sounds like something that could be badly implemented, but there's nothing unreasonable about the idea in general. Oversubscribed services are par for the course. If your neighborhood's uplink is saturated during a period of heavy usage, do you really expect each customer to get 1/N share of the bandwidth, or do you expect the customers paying for the 100Mb plan to get up to 5 times more bandwidth than the customers paying for the 20Mb plan? Either way, it's obviously not suffering from the kind of unfairness that gives preference to certain usage patterns over others, and it doesn't involve any extorting of upstream content providers or other form of double-charging for services.