alt Hacker NewsThe implementation of the idea looks more like a kiwifarm egg than a facebook egg.
Thinking about Anonymous posting about non public figures is perturbing. If the poster can't be made responsible for the post, then the platform and the platform of the platform (and so on) are in line. That is: new website, then the hosting servers (and so on)
DMCA is a pretty good model for this sort of thing IMO. You take down the post, notify the poster, and if the poster wants they can have you put it back up and tell the original complainant "sue me". If you don't follow that process they can sue you instead.