What should be the approach for banning offending users from your site? The only way I can think of to identify them is their IP. In the world of proxies and shared ips, how to ban one user, with out impacting other legitimate users?
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.
