There are many difficulties in adopting a scheme such as DSR. Here are a few negative arguments that must be countered, however:
It is too expensive to charge
Perhaps the most dramatic departure of the Internet from classic long distance communications is the way it is priced. For most of the 20th century such communications were deemed natural monopolies and bureaucrats, rather than the market, set the prices. Phone companies were indeed limited to modest profits, at least in most countries, but they had relatively little incentive to decrease their costs as that would lead to only temporary extra profits. The contentious arrangement between the telcos and regulators requires detailed billing information to be delivered to the customer. When the cost of a long distance call was a few dollars it made sense to send the customer a detailed bill. Today, however, it seems that the telcos spend 10 cents, telling you that you have cost them 0.01 cents to place your call and that therefore they must charge you 12 cents in order to make their fair profit. When I turn on a 60 watt light for ten minutes the electric meter measures this and charges me $.001. It is not an onerous burden and I don’t need a detailed bill! DSR charging is more like the electric meter. The time is close, I think, when I can have a leisurely voice conversation with someone in another country without thinking about the cost. Add video, however, and it may be necessary to have some sort of incentive to kill the stream before I go to sleep.
I may get a bill the ruins me financially
This is a real problem with simple solutions. My favorite solution is a contract with my ISP, who I pay for DSR charges. The contract limits my liabilities to a specified amount that can be increased only thru an authenticated transaction. My ISP will not relay packet values amounts beyond that limit. Even simpler my ISP arrangement may always require a positive account balance. I can then never get a bill from my ISP just as I now never get a bill from my pre-paid cell phone provider.