Note that this is actually one of the things Anubis does. That's what the proof-of-work system is, it just operates across the full load rather than targeted to

Note that this is actually one of the things Anubis does. That's what the proof-of-work system is, it just operates across the full load rather than targeted to a specific user's load. But, to the GP's point, that's the best option while allowing anonymous users. All the best, -HG