Psh.... just don't wear goggles, they're for wussies anyway.
....The fan thing works wonders, I've seen it used several times and I'm gonna set up a pair of goggles like that m'self, but you need to have fairly deep goggles for it to be used, (you can't really do it with your bolle's, but paintball goggles are a prime candidate)...
Either way, for anyone who's in the forces, the anti-fog wipe you get with your ballistic eyewear works great. I was actually impressed with it.