The global police state is coming...
"Attempts to banish anonymity from the internet won't affect those savvy enough to bypass it, would cost billions, and would have only a negligible effect on security,"
The same is true about the real passports, isn't it? The savvy criminals use forged or stolen passports. This hasn't prevented the governments from mandating passports for their citizens, because it means that the vast majority of people are more easily monitored and controlled.
Which is precisely why something like this WILL be made mandatory on the Internet. Not because it will stop the criminals (it won't) - but because it will allow the governments to suppress dissenters and wikileakers better.