Thought I'd add Collin Moshman's thoughts on this as they were pretty interesting:
(from
http://teammoshman.com/?p=9665)
A lot of people are still talking about the face-up quads fold in One Drop. I don’t have the exact details, but will reconstruct the action as closely as I can to start the discussion.
Blinds: $6000-$12000-$2000
Preflop: Dwan raises to $32k (position unknown), Mikhail Smirnov calls in SB with

, John Morgan calls in BB.
Flop:

(Pot: $114k)
Action: Smirnov bets $50k, Morgan calls “quickly,” Dwan folds.
Turn:

(Pot: $214k)
Action: Smirnov bets $200k, Morgan insta-calls.
River:

(Pot: $614k)
Action: Smirnov bets $700k, Morgan shoves $3.4M, Smirnov folds face-up.
Analysis: Smirnov afterward says this was a “very easy fold,” which I think most would agree at least intuitively is a strange comment to make here.
I agree that the river shove indicates huge strength, particularly from a tighter player. So let’s assume that Morgan is almost never bluffing or randomly shoving without a purpose. The only hands consistent with the river action are, let’s say, JJ, KK, and Ts9s.
So now let’s look at the earlier streets. Ts9s is the most consistent with the preflop action, but one aspect of the flop and turn are inconsistent. In particular, quick calls are rarely monsters. Everyone agrees that Morgan insta-called the turn. It’s just super unlikely he makes a quick flop call with the nuts and doesn’t even consider raising, and it’s even more unlikely on the turn in a million dollar tourney in a large pot holding the stone nuts facing a large bet. Same with JJ, both of those hands are strong enough that turn snap-calls are unlikely. Definitely not impossible, just inconsistent with the timing.
So the alternative is KK. While Morgan would most likely 3bet KK preflop, a cautious amateur could have decided to avoid playing a large pot OOP against Dwan with a fairly deep effective stack, even with a monster. The quick flop and turn calls would then be less inconsistent with a hand like KK, as would the river shove.
So I believe that KK is Morgan’s most likely holding in this spot.
But let’s make the most generous assumptions we can for Smirnov’s fold:
Morgan never holds any hand besides KK or Ts9s (including 0% chance of JJ).
Morgan’s actions are equally consistent with KK or Ts9s.
There are three KK combos and one Ts9s combo. Therefore Smirnov has 75% equity against Morgan’s shoving range while getting around 7:4 and therefore needing only about 36% equity. Alternatively, Smirnov would be paying $2.7M for 75% equity in a $7.414M pot, for an equity gain of around $2.9M chips.
Smirnov therefore forfeits reasonably close to a million dollars in equity by folding there, based on the above assumptions. For that reason I believe this fold to be one of the most significant mistakes equity-wise in the history of tourament poker.