They don't really need a buffer, they just need reasonable overage charges.
I pay $10/GB if I go over, and that's pretty reasonable. I've exceeded my plan in the past and the additional charges are entirely sane.
No carrier is getting negative press because of a $10 overage charge, or even a $50 overage charge. They get negative press when they charge $10 for 30kB for roaming without warning the customer, and then the customer gets a bill for $15,000.
I pay $10/GB if I go over, and that's pretty reasonable. I've exceeded my plan in the past and the additional charges are entirely sane.
No carrier is getting negative press because of a $10 overage charge, or even a $50 overage charge. They get negative press when they charge $10 for 30kB for roaming without warning the customer, and then the customer gets a bill for $15,000.