WoWheads! Are you playing the latest expansion yet, with all its fiddley new talent trees and raid bosses and PvP specs? No?! Well, you soon might be, since Blizzard's mastery of all thing addictive is seeing them put a new plan into place that may get you hooked even against your better judgment. After all, what's a better price than "free?"
The "account revival trial" is a time-honored technique for MMOs to market to their once-and-former fans--folks who already have investments there, in the form of decked-out characters or just lots of time in guild chat. Who better to target with a free 10-day pass into the new Cataclysm content than players who are or once were active in Wrath of the Lich King? If you're one such player, it definitely wouldn't hurt to jump in and see what they've changed - even just to run around the starting areas and try to catalog all the pop culture references in the quests. (Protip: You can't.)
The FAQ advises that the actual Cataclysm content requires a level 78 character or above, but those who played Lich King should have no trouble getting close to that in the 10 days, were they to take the plunge. Or, you could try taking one of those new goblin or worgen characters for a spin.
The trial page doesn't list an expiration date, but it might be good to jump on this before the holidays are over, if the daily grind has left you any time for the nightly one!