My opinion ...
There should only be unlimited (truly unlimited) plans.
At the gas pumps are meters for measuring the amount of gas dispensed. This is verified by an independent 3rd party. This is prevent gas station owners (etc) from cheating customers.
If you're paying by the mega byte, then this measurement should be confirmed by an independent 3rd party. With data like this, this is a big problem.
But not for unlimited plans.
So either the carriers get measured to independently confirm data usage or ... unlimited plans only.
an interesting point
I'll take it further. Imagine a person goes to the gas station and pays a fixed rate, regardless of how much gas you get. Of course, you would not get gas for less than the cost. You would always pay for, say 30 gallons, yet would get between 10 to 20, 25 gallons depending on individual habits.
I want to pay for exactly what I get, no more or less. When I purchase a book or whatever from a store, I know exactly what I'm paying for.
It seems to me that there is push to incur regular cost for services from lots of different business. (monthly cell services, monthly game costs)
A service isn't the same as a book, but I don't want to pay for something I'm not getting.
I ulimately have choice and can refuse to have cell service. This is a simplistic thought though, and doesn't address a legitimate issue of getting what you pay for.