There are some interesting ideas to work around the problems with this method in the comments, such as hashing the ip with a secret string on the link to stop o

There are some interesting ideas to work around the problems with this method in the comments, such as hashing the ip with a secret string on the link to stop others making you ban all your users. And also sorts of other stuff - even putting a CAPTCHA on the ban page as an escape method. But in the end I think the method is flawed: 1) a singled infected computer on a network could take out a large number of users. 2) any thing doing prefetching will cause them to be banned. 3) there is a risk of taking out valid bots, and verifying them correctly is just too expensive for a large site. My main issue with bots is their spam, so I just use tools like Akismet to keep that under control.