I expect it's either because World of Warcraft players are giving it a try or there are server crashes kicking everyone out of a zone at once and they're all trying to get back in at the same time.
Back in the day, some MUDs would exaggerate the number of people in a queue (or even invent the fact that there was a queue), but this isn't something I believe game operators do any more. Amazingly, not all modern developments in the treatment of players are worse than they used to be.