A truly nice add-on. I've been using it for like a month or so.It tells you the reputation of the website so you know what you're up against. The reputation is decided by the community who uses WOT. That's the nice thing, you can vote a website yourself, in four different sections - Trustworthiness, Vendor reliability, Privacy, and Child Safety. This add-on is for both Firefox and IE, and probably works with flock too. It also shows you the rating before entering the website for popular search websites like Google.
You can get it from their Main Page or from the Firefox Add-on's.
For the rating part - each user actually has some kind of trustworthiness rating from WOT, which determines the weighting of their vote. New users and unregistered would have a low weighting, and therefore would not affect the rating much. The performance hit is minimal. Hope you guys like this add-on.