The concept of "unlimited" plans is obviously a fiction, but there are problems presented by selling customers a fixed monthly data allotment because people who download at off peak hours will unfairly pay as much as someone who downloads during peak hours, and regardless of the time of day someone who downloads from a cell site with a huge excess of capacity will be penalized just as much as someone who downloads from a cell site that is breaking under overwhelming demand.
The best solution is for the cell phone companies to sell customers 'shares' of bandwidth. It would work something like this:
With your cell phone plan you own one 'share' of bandwidth and you are allowed to download 10 Gb/month of peak demand data. You have an unlimited monthly allotment of non-peak data that you can download.
Say that the cell phone company defines 'peak' data usage as anytime an individual customer for an individual cell site is unable to download at a rate of at least one Mbps.
Now say a given cell site has a capacity of 10 Mbps. If two different customers are accessing this site simultaneously (each has one share) then each one will be able to download at a rate of 5 Mbps. This cell site obviously has a lot of excess capacity - neither of these two users will have eaten into their 10 Gb/month data allotment.
Now say that the same cell site has twenty users - each user's share will come out to 0.5 Mbps of bandwidth. The data that is being downloaded will be deducted from their 10 Gb/month allowance because the available bandwidth per share is now less than one Mbps.
What happens when a user exceeds their monthly allotment? They get throttled down to... well let's say 0.5 shares. Now when they download they will only get 0.25 Mbps at the same time that other users are getting 0.5 Mbps from the same site.
Users who want more capacity can purchase more shares from the wireless provider.
The cell sites should give real-time feedback to the smartphones when the cell site is operating at peak capacity and deducting from their 10 Gb/month limit.
The FCC will need to put out some rules to prevent the usual predictable abusive wireless provider behavior. We don't want AT&T to suddenly charge you one dollar per Mb that you use in excess of the 10 Gb/month limit. In my view it is criminal when companies generate revenue via 'gotchas' instead of honest practices.