That's not entirely surprising. There was a post (I think I saw it on HN but I can't find it now, dangit) that put forth the idea that unlimited data plans were bad for consumers, because then consumers' and providers' interests are unaligned. Once you pay for an "unlimited" plan, it becomes in the network's best interest for you to send as few bits as possible. Consumers should actually prefer pay-per-use plans, because it means if the network is down, the service provider doesn't get paid.

Of course, there are many other variables involved, and obviously everyone has different usage patterns.