I just got an email:
Take a trip back to Azeroth with 7 days of FREE game time! Simply click below to claim your time and experience all of the latest improvements and additions to World of Warcraft®... but act fast, as this offer will expire on Mar 22, 2011.
It looks incredibly professional, and looks very real. The only suspicious thing is the link to claim 7 free days of game time, which seems to be a squat of battle.net (you can see the actual link in the revision history for this post if you're so inclined).
How can I tell if this an actual Blizzard thing, or if I'm being phished?