Assuming a realm's participation in realm wars is optional I can support this.
My major concern is that member heavy realms - Foxtopia (59 members), Frogtown (34 members), Celestis (34 members), etc - would be able to rapidly conquer less populated realms. Ultimately this would lead to most of the small realms being conquered or forced to join a larger realm.
While the inexperienced may believe this is an advantage, in reality it leads to heavy stagnation and sincere hostility between players. If you require a proof of hypothesis, research the alliance coalitions of EVE Online. They control the full-pvp areas of that game, preventing new and small factions from establishing themselves.
In recap - If a realm's participation is voluntary, then I support realm wars. Otherwise I believe it will be detrimental to gameplay.
EDIT: How exactly would one conquer a realm anyhow? I wasn't around for 2.0.
