I,m sure they would save themselves a lot of heartache by setting a fair llimit and perhaps a multiple tiered pricing structure for those that want more than the ocassional email, they are after all the provider of the service and its for them to be open and honest in their dealings with the consumer.
One day perhaps a partial refund system could be operated for those barely use the service, although I dont see this occuring anytime soon as this sort of customer out-numbers the "limit busting" users by a massive majority.