Well, actually, Shadow, we KNOW they won't work out if their use is too widespread. That's obvious, and something anyone could tell you. What we don't know, is that, given all the downsides to using one, enough people will use them to cause issues. I'm thinking here, if your syncing takes to long, your opponent is given the first point of the set, and you still don't get to pick second, and if you lose because your Wiimote desyncs, you lose, period.
Edit: Chi's Finest, I REALLY don't see why they should be banned over the chance someone might lose by their own fault on account of desyncing or low batteries, if they're not widely used. ANYONE bringing a Wiimote should accept the chance that if their batteries run low, they're out, and that if they see too many other wiimotes and use one anyway, causing a desync, they're out. It's common sense. Just because the rules might ALLOW Wiimotes, doesn't mean you're being told or forced or even asked to use one. It should be made painfully clear that you run serious risks by using one.
I definitely think for really large events they should have an outright ban. The larger you get, the more oddballs are going to show up with Wiimotes. But a standardized ban on them everywhere and in every tournament would be silly, especially at this point before we even know if they're popular enough to interfere with each other.