I don't think this would be the greatest idea.
If it were to be completely open, as in anyone could post watchlist names, people won't follow the rules of putting only the cheaters/fuckovers/etc. on the list. You're likely to end up with a very lengthy list of people that some people just don't like, and you're probably going to find some people that might not be liked on the forum but have been completely honest and legit in game. This list could get to the point where it would need someone (or multiple someones) to mod it on a 24 hour basis.
The solution to this is to make it mod only. I have a problem with this as well. The morality of ingame issues is completely up to whoever is in charge of the thread. I may consider a ninja lot to be worthy of being put in the list where the mod for the thread would disagree and say all is fair and this person would be free from the watchlist (I highly doubt this to be likely, but you get the idea). The other problem with having it mod only: Don't these mods have enough on their hands as it is to have to constantly keep up with every single FB post and make the decision as to whether or not put someone on the watchlist?
Just thought I'd share my own personal thoughts on this...