Easy proxying means rate limiting doesn’t really help all that much to defeat bots. And then if you do something like blocking or severely restricting something like Tor (the world's largest open proxy and hence, primary abusive traffic source; something which it would make sense to throw extra bot walls in front of), privacy and accessibility advocates jump down your throat.

This is a no-win situation. I’m not convinced it’s possible to have ones cake and eat it too, here. Someone upthread said “security, privacy, accessibility, pick any two”, and I have yet to see any evidence of a third option.