Once again, the bulk of the day's recap was inadvertently captured in the mid-day-commentary.  Feel free to read that instead of this if you want.  If you're not into clicking links, here's a redux:

As expected, the evaporation of liquidity ahead of the Thanksgiving holiday week began today.  It was most pronounced after the European close.  The imbalance clearly favored sellers in today's case, making for a quick spike in yields and a quick drop in MBS prices.  Most lenders repriced negatively.

One additional factoid has come to light since the mid-day commentary, and it provides a strong piece of evidence for today's imbalance favoring sellers.  The Commitment of Traders report comes out every Friday, conveying the official positions held by traders as of Tuesday.  All across the Treasury spectrum, traders were adding on to short positions (as of Tuesday).  Then, note the past two days, we've been talking about "short-covering" as a justification for gains.  It stands to reason that traders would be exiting positions heading into a known period of illiquidity, and this is confirmation that a majority of those positions were short.  It also stands to reason that the morning hours would see the most short covering due to the relatively higher liquidity while Europe is still open.  The conclusion is that the strength was indeed driven by short covering, and the selling was indeed driven by a sudden absence of buy-side interest.