Why did Bitcoin transaction volume heavily increase in November and December of 2011? Looking at this chart:
http://blockchain.info/charts/estimated-transaction-volume

It's clear that the amount of bitcoins moved between November 14th and December 12th of 2011 was much larger than any previous month, even compared to the big boom in September.

The number of transactions is about the same as previous months. This implies a few big transactions or generally large transactions. What is the reason for this?
Could it be Christmas shopping? People who have thick bitcoin wallets, needing dollars to buy Christmas presents? Many online retailers make half their money by selling Christmas presents.