I doubt that you can run Netflix on any single server no matter of the webframework. Besides that Netflix itself is a Rails user for many applications (most of them for internal purposes).

It seems the bottleneck with netflix would be storage requirements and number of PCIe lanes for extra NICs. I really don't see how, "This framework couldn't run a site that accounts for up to 40% of internet traffic at peak hours on one server; clearly it's terrible!" I like scaling as much as the next guy, but Pareto dictates (as does experice) that most stuff is simple business logic with an interface.