Toby,
But this largely a self regulating promise. If the cell phone companies were doing this - if you stay inside the plan - you are home free - but otherwise they surcharge you for overages at 10x the plan rate!
I'm not sure I want to perpetuate that ugly model and world.
It's OK if its purely for predicting future load patterns.
I much prefer the reverse plan - which is you get credit back for using less!
DW