I understand the potential "abuse" part, but I'm just saying that I don't understand why they limit one and not the other, when both are capable of exceeding the 5Gb. I have a few friends who live by their iPhones, and they seriously hit 6-8Gb worth of use in many months (constant streaming of Pandora on the highest quality setting, lots of 'net use, etc), yet their is no overage charge on that, but if you do the same on a data card, there is. "Mass consumption" is mass consumption, no matter what device. 5GB on one device is equal to 5GB on another is all I'm saying. And all of this is completely off the OP's topic.
And by the way, I'm not arguing with you or anything like that. I agree with most of the things you've said. Just mainly throwing out thoughts and questions that pop into my head about this as I read the thread.