However, I don't think it follows that Netflix must be treated any differently. The customers are the ones requesting the data. To the extent that anyone (once at capacity) should bear a cost, it should be the requester -- either through a higher fee or a smaller fraction of the pipe.

In practice, that will mean "the more Netflix [or anything] you use, the slower your service". But you shouldn't "short-circuit" the process and just start punishing Netflix's packets directly just for being Netflix. Rather, it should be "this customer endures this cost [broadly defined] for using this much, regardless of what it was for".