If you type "DM", 99.99% of the new players coming from retail, that never played during Vanilla, are going to assume you meant Deadmines, and if you tell them that DM means Dire Maul and VC means Van Cleef, they are going to ask you what a Dire Maul is, and who Van Cleef is.
 
	It's a neat tradition to call it "VC", but DM has meant Deadmines, in retail WoW, for quite awhile, so no one is going to know what the hell you're talking about using VC.
 
	On a side note: the Germans calling tanks Damage Takers has gotten a little out of hand, though.