A report by Ericsson predicts a tenfold increase in mobile data traffic in the next five years. That increase has caused carriers to rethink the unlimited data plans, and most have already stopped offering them. Some, like AT&T, are even throttling users that have grandfathered unlimited plans.
It is a battle between the marketing department and operations. When a carrier can say "unlimited data" it grabs attention, especially today. In talking with carriers though, FierceWireless is told that the unlimited plans are an "unsustainable model."
European carriers are doing what American carriers have done, which is to separate data plans from voice and text. The number of minutes purchased and amount of data purchased can be done independently of each other. This allows users to tailor their monthly fees to their needs.
Having fixed data plans isn't that big of a deal for most people. The issue is users are too often faced with overage charges with little or no explanation from the carrier. You don't have to search too far to find examples where devices, smartphones in particular, pull down a few hundred KB or more of data overnight when the phone is not in use. That adds up over time.
Many users also have multiple email accounts and apps that run in the background that consume data periodically. It is difficult for a user to know how much data a given activity will consume. Unlike voice billing, which has detailed statements available for every number you called with the exact time, data plans have no such feature. You know the carriers are recording this information though, as they have turned this kind of information over to law enforcement as needed.
Why then don't carriers make this data available to users on their bill? Instead users are left guessing when their phone consumes a lot of data when not in use or are unable to understand how they went over their data allowance in the first three weeks of the month.
With unlimited plans, it doesn't really matter. With limits though, this download information would be a useful tool for consumers. Without it, it is an opportunity for carriers to get some extra revenue with little or no recourse available for the user.