All users. Just like just about everything else, the more of it that is used up the more the consumer of that good or service should pay for it. Water and electricity users pay more when they consume more. I'm at a loss as to why data usage should be any different. The providers will compete with each other and risk becoming regulated utilities if they abuse the free market.
The companies that sell the last mile do have competitors. Cable, cable over-builders, telephone, wireless, electrical utilities, dish companies and others all have developed technologies and/or invested in extensive infrastructure. The wholesale providers of fiber or broadcast spectrum have the least competition and have built their delivery systems over government property... so they'll always be regulated to some degree and unlikely to be able to exploit abusive pricing practices.
The more that Netflex and similar users utilize the infrastructure the more they should pay. If that means their customers must pay more, then there's really no problem with that. The Comcasts, Charters, AT&Ts, Verizons, Speints, T-Mobiles, US Cellular/TDSs already charge their customers a variable rate based on capacity.
The residential waste disposal industry should have a more usage based model too. The household producing 10 pounds of trash a week gets charged the same as the one that puts 300 pounds a week into the landfill.