There are a million reasons why and ways to block someone from visiting your website. When you put up a block you may also be blocking someone who wants to visit your website. How do you balance between that and stopping visitors you don’t want coming to your website?
There are many reasons for blocking someone on your website
Someone could be spamming the comments section on your blog posts. There are many options for this (affiliate link) and banning is one of the more popular options.
If an account gets hacked into or stolen then you will want the actual account owner to contact you. If you block the account then you can be sure that the account owner has to contact you to get the account back.
You may not want people using any sort of proxies to access your website. If you redirect people to their local site, or do relevant privacy banners you want the people who need to see that. You may also have servers located around the world and want people to be directed to the closest server.
How do some people bypass the ban?
Someone can change their IP address to go to your website.
If your website has open registration then someone can create a new account to bypass your ban.
Your site could also be archived by any of the arching sites. These allow anyone to view a history of the website.
There is a fine line between forever banning someone, and not banning them at all. What that fine line is depends on many of your own factors.
Banning someone could involve a time-based ban, or trying to ban something that is unique to them.
Bans online are usually not 100% effective as things keep changing. Whoever handles the banning on your website will need to keep on top of banning the right accounts.
Why shouldn’t you do permanent blocks?
Nothing about a website visitor will be 100% unique. Which means if you want to block one person you will most likely be blocking more people.
If you go to a website and are IP banned then contact the website by email to get your IP address unbanned.
While permanent blocking is a fast and easy way to do blocking. It could also seen as lazy that you would rather do a block, than find a better way to block the one website visitor.
If your website doesn’t already have a website banning policy, then get one started.
Finally, how or when you ban someone depends on many, many factors and each website will have their own way to do so.