"Many users have access to hundreds of machines with unique ips and have the scripting resources to automate nearly undetectable sock-puppets."

Nothing is "undetectable" if you have the right software and skilled programmers to do the job. Take cellphones for example. They all have not only unique phone numbers but also unique IMEI numbers. It is therefore near impossible to setup multiple accounts using a single SIM phone, and even less so, if you were to require 2FA such as Google Authenticator.

The same can be done with desktop PCs or laptops. All you would need is software which detected both the user's IP address and the computer's hard-drive's serial number, and then match those to the member's account. Any attempt to login without this match, would be denied until such time as the user could show that he either changed computers or service providers. Once he did that, the new matching info would be recorded in his account, and the old info deleted.