What a terrible idea! Not though trough at all, which might not be much of a surprise given Blizzard's 'fire and forget' introduction of RP realms.
Their seeming obsession with never merging realms to reflect the fact that their game has (far) less than half the people it once hosted is causing all sorts of problems; from anonymous groups who never meet again to now these cross-realm zone shenanigans wrecking havoc on some of the last remaining realm-based communities.