False positives are extremely rare- every website is reviewed by a human being before being added. The bigger issue (which was addressed a bit in the post) is when we have to block something that isn't meant to be malicious, such as a hacked site. Obviously people want to be delisted as quickly as possible.
When a website is cleaned up we'll typically notice that ourselves, but if not there's a place on our forums dedicated to false positives and our support team knows how to handle the requests. When a website is genuinely clean it's generally delisted in the next update, which is often within a couple of hours.
