A good bit of the discussion seems centered on how effective the design is in getting all of those wheels to work (e.g. no chains, etc). The real question it seems is, why have all of those wheels? The only effective answer I have seen so far is to avoid "high centering" when going up ramps.
The common response to all of those wheels is "they would give lots of traction". But will this approach be more effective in doing so than one with fewer wheels? The simple model of friction (which is what traction really is) states that maximum friction force is the coefficient of friction multiplied by the normal force (i.e. the weight pushing down on the wheels). The coefficient is a function of the material of the wheel and the carpet. Assuming that there is a given weight for the robot, this weight would be distributed over the wheels, and if there were more wheels, there is less weight per wheel.
The short story is that adding more wheels in this case does not add more traction. The fallacy that it would comes from the "outdoor scenario", where terrain may have low coefficients of friction (e.g. snow). The idea here is that more drive wheels can avoid the situation where wheels slip, and the friction coefficient lessens (going from static to kinetic friction).
Wikipedia has more info for those interested.
http://en.wikipedia.org/wiki/Friction