The site features a list of countries who qualified for the World Cup tournament and Personas for each of them. Firefox users will compete against one another by using the Persona of the country they support.
Currently, Argentina tops the list, with Brazil not far behind and gaining fast. Looking at the bottom of the list, I can’t help but feel sorry for North Korea, who will almost certainly rank last due to their heavily filtered internet.
Update: And here’s the official Mozilla announcement.