Peter Van Doren points me to some revealing passages in a new article in the Journal of Economic Perspectives. In "Subsidizing Creativity through Network Design: Zero-Pricing and Net Neutrality," Robin S. Lee and Tim Wu caution against tiered pricing for Internet access services, writing:
[U]nless sufficient bandwidth and quality of service can be guaranteed for the "free" Internet, there is a risk that . . . tiering will serve to sidestep de facto prohibition on termination fees. . . . [A] priced-priority system could simply become a de facto fee charged for all content providers if the "free" Internet was of sufficiently poor quality and consumers shifted their usage behavior accordingly. . . . [T]his might dampen the introduction of new content and services and eliminate the subsidy for content innovation currently provided by net neutrality.
Locking in net neutrality by regulation would lock in a subsidy to content providers. Lee and Wu prefer it, and many of us may like the results, but it's hard to call a subsidy regime "neutral."