If you check our Monthly Update thread for November [webmasterworld.com], you'll see a lot of buzz about a possible Panda Update around Nov 21/22, or right on the Thanksgiving Holiday in the UD - for example:
I have woken up this morning to signs of a Panda update (UK). Is anyone else seeing this? -petehall
Barry at SERoundtable reported on Nov 20 that Google said a Panda Update was coming in 7-10 days... however, now they have confirmed that it actually rolled out on Nov 21! I guess the holiday scrambled someone at Google, but now we do have official confirmation about Panda #22 Update on November 21.