Ask HN: How to ban users from your site?

Proxies make it impossible to ban anyone. You can detect open proxies like slashdot does and prevent anyone from using any open proxy, but offenders can still use non-open proxies. You can charge for access like somethingawful does so that when you ban someone's account they have to pay $10 or so for another. That's about it.

You can't really ban users from a website that's free to the public. All you can do is bore problematic users into going away.

These guys do it all day long.

www.iovation.com