[Genjiro]

We played evil side on SZ, and the racial imbalances of shit like ogre+iksar vs other races made it an easy choice, since from a pve standpoint they were clearly better (ogres as tanks) and iksar as any class they could choose.

WoW is trying to combat it in places in WotLK, such as Wintergrasp by giving the smaller side a scaling buff if they are outnumbered and so forth. That's about all you really can do, and provide huge incentives for underpopulated sides. Faction increases, xp increases, easier to build castles and such if thats the kind of world you are playing in....if you provide enough benefits people will reroll or new players will be more inclined to choose that side to start with.