Maybe 2-3 years ago. Pretty sure it was IP based. CF drops you on a shared IP, its hit and miss of you end up on an IP next to a bunch of dodgy sites or not, do a reverse IP lookup to find out what else is running on your IP.

> It would be insane to keep this practice up.

What's the alternative?

Oh yea, did CF ever fix the domain hijacking issue for deleted sites?