LAST EDITED ON 12-02-08 AT 06:32 PM (EST)Not sure exactly how it works, but I'm pretty sure some of the eliminated teams continue on, following the same path as the racers still in the game (tasks and all). That way if someone sees them, nobody will know who is the final 3 or whatever.
They also use some of the eliminated teams to film the race to the finish mat several times with different outcomes, so if anyone is watching, they won't know who actually won.