Hi,
I'd like to suggest two solutions to the blocking of dynamic IP addresses or proxies that may affect innocent users.
Solution #1: IP address blocks should expire after n days unless renewed by someone. That way, instead of forgetting to unblock people, at worst we forget to re-block them. In my opinion, it's better to fail to punish somone effectively than to punish someone who's innocent.
Solution #2: We should give blocked users a way to re-gain access to the site, namely by creating an account. I don't know if this is currently possible, but it should be. We can block accounts a lot easier than IP addresses. So we could basically say on the block page: "Because IP addresses cannot be reliably linked to individuals, it may be that you receive this message in error. In that case, or if you want to change your behavior, please create an account and sign in, and you can continue to use Wikipedia."
We might still reserve complete IP&account bans for those who abuse the account "backdoor", but this should be the exception, not the rule.
This would make our security softer, and hopefully more effective.
Regards,
Erik