I dont know who else this is annoying, but I hate having to mail my characters gold, or items that I buy them because they cant access my mains gold supply. This seems like a "duh" thing for blizzard to fix. Blizzard is trying to push people towards multiple characters for Cataclysm, and this would make it more appealing. Also it would free up server space by taking out unnecessary mail between toons.
Let me be specific: Server-wide, faction specific. This way it doesnt destroy the economy.