It's easily been over a decade since this has happened but MK @ WDW hit absolute capacity which means NOBODY gets in.  No resort guests, no AP's, nobody.  I've been there over two New Years Eve's and July 4th and hit phase 2 every time.  Let me tell you that 2 1/2 hour waits for nearly every main attraction and even worse, 1+ hour lines just for food is no fun so I can't even imagine this!  Yikes

And go figure, they recently laid off a ton of cast members.  The only thing I can think of is they under estimated the response to their buy 4 nights get 3 free deal and perhaps also something with the timing of Spring break.

I found the news here - http://forums.wdwmagic.com/showthread.php?t=426433

Yup, phase 2 was just insane.  You couldn't move anywhere.  A trip to the bathroom literally took 30 minutes.  Basically, you camped out in one area and enjoyed people watching until the fireworks started.

This year we switched to EPCOT so we could at least enjoy an alcoholic beverage while waiting it out lol

One of the members in that thread posted the criteria for each closing phase.  Apparently Hollywood Studios came just as close to closing as well today.  I don't think EPCOT ever could just because of it's insane size and Animal Kingdom, well, wishes it could hit phased closings lol.

EDIT:  Just found the post.  Here are the phases:

Phase 1: Guests with Magic Your Way base tickets, one day tickets, guests with no admission, and CMs using a main gate are turned around at the Auto Plaza.

Phase 2: Only resort guests, AP/PAP, Park Hoppers, guests re-entering the same park admitted, ONLY if using a taxi or resort transportation. (Auto Plaza is closed)

Phase 3: Only resort guests and AP/PAP admitted. (Only resort transportation)

Phase 4: Closed to all guests. (No incoming transportation)

Wow, I heard about this but didn't know how legit it was since I was just told a few weeks ago that they won't close the gates anymore ever since that riot in Japan or wherever. I was there on a Friday (MGM) last week and it was busy, but no where near as busy as Christmas time... hopefully this week coming up wont be like that with Matt flying down.