Check the fine print on an "unlimited" plan and you will see there is a cap. I believe most are in the 5GB range. The TOS also specify services that you can not use which could limit you. 5GB may sound like a lot until you have to patch your OS, download some software, or stream Hulu or Netflix. The speeds are also usually well below even a streamlined DSL. I would call your cable provider. Some offer slower cable connections than they advertise.