Of course, it could always be a three-team alliance, with no backup team (subliminal message: "build 'em robust, or else!"). Or a single team with two alternates (subliminal message: "this game is so hard that we expect you to thrash two robots in the finals"). Or a set of three independent teams ("We are sick of alliances after all the whining last year.* It's a free-for-all, and the last three standing win!"). Or the ultimate evil option - a four team alliance, and the alliance has to pick which team has to stay behind for the benefit of the entire alliance (subliminal message: "do you REALLY understand the
Nash Equilibrium in the general class of non-cooperative games?").
Just because you know something, don't assume that you actually know something.
-dave
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*colluding to agree to not collude is still collusion