I was working at eBay/PayPal at the time, and we were finding a bunch of new phishing sites every day. We would keep a list and try to track down the owners of the (almost always hacked) sites and ask them to take it down. But sometimes it would take weeks or months for the site to get removed, so we looked for a better solution. We got together with the other big companies that were being phished (mostly banks) and formed a working group.
One of the things we did was approach the browser vendors and ask them if we could provide them a blacklist of phishing sites, which we already had, would they block those sites at the browser level.
For years, they said no, because they were worried about the liability of accidentally blocking something that wasn't a phishing site. So we all agreed to promise that no site would ever be put on the list without human verification and the lawyers did some lawyer magic to shift liability to the company that put a site on the list.
And thus, the built in blacklist was born. And it worked well for a while. We would find a site, put it on the list, and then all the browsers would block it.
But since then it seems that they have forgotten their fear of liability, as well as their promise that all sites on the list will be reviewed by a human. Now that the feature exists, they have found other uses for it.
And that is your slippery slope lesson for today! :)