I've always wondered if you could combat via referal-only sites. To get in you need to achir your humanness on someone else's account. If an account is found to invite too many spammers, robots, or otherwise it is banned or disallowed to invite more accounts.
I'm sure you could still manage to make "fake" accounts but it would be much more difficult, and linking them together would be much easier.
Of course starting a site like this would be very difficult. But maybe you could start without it then add it in once you get to a decent popularity such that many people can find a referral if they need to.
Of course it is a much smaller site so it isn't clear how effective this strategy would be at a large scale. Even a referral-based site approaching HN levels would be very interesting to see.
I'm sure you could still manage to make "fake" accounts but it would be much more difficult, and linking them together would be much easier.
Of course starting a site like this would be very difficult. But maybe you could start without it then add it in once you get to a decent popularity such that many people can find a referral if they need to.