Check it down or not??

Here’s a common tournament situation:
One short-stacked player pushes all-in and
is called by two or more larger-stacked opponents. Among
experienced tournament players, there’s an unwritten rule
that both of the bigger stacks will just check the hand
through all the way to the river—maximizing the chance
of the short-stacked player being eliminated, because
he’s competing against two other hands at the showdown,
instead of only one.

In practice, this sort of thing happens all the time during
tournaments. There is some question of whether or not this
unspoken agreement to “check it down” anytime a third
player is all in might actually be a form of implicit collusion.
In a sense, the two checking players are ganging up on the
all-in guy, which technically fits the definition of collusion.
But unless these two players actually discuss the action of
checking it down between them, for all practical purposes
they are simply pursuing a time-honored tournament strategy.
It’s a strategy so commonly embraced among tournament
players that anybody who doesn’t follow this practice—who
decides instead to bet and push the other live player out
of the pot—might find himself on the receiving end of some
angry comments and nasty looks from the rest of the table.
Especially if the all-in player ends up surviving as a result.
This debate boils down to what matters most to you as
a tournament player—the chance to eliminate an opponent
from the competition, or the chance to win whatever chips
are in the pot? The actual merit of this play depends on the
specific situation, and several factors play a role here.
First, how far along is the tournament? Has it gotten
into the money stage yet, or even close to it? If the answer
is yes, then eliminating opponents takes on a far greater
importance than it does when the tourney is still in the early
stages. Early on, it’s all about surviving and building up your
chip stack. Knocking out opponents is a secondary consideration.
But once the tourney gets into the money, every
eliminated player guarantees more cold hard cash for each
player who remains. And that’s almost always worth more
than any single pot of tournament chips.
Something else to consider is how many chips, if any, are
in the side pot—the pot the two remaining players are competing
for. If there’s nothing in it, or next-to-nothing, then
there’s little point in betting at it just to push the other live
player out. The main exception would be if you actually hold
a good hand which you are reasonably sure will beat the
all-in player at the showdown. Now you’re betting to protect
your equity in the main pot, so the other live player won’t
draw out on you.

Even here, there’s mucho disagreement among tournament
players as to what “good” hand would in fact be good
enough to merit a bet in this situation. Some players feel
that only the nuts—a hand that is virtually an iron-clad guarantee
to beat Mr. All In—is bettable here. While others feel
that a hand as weak as second pair would be worth a bet,
as long as it gives the bettor an improved chance to win the
main pot. This standard varies all over the place, depending
on the individual and the particulars of the situation.
The one universally-agreed-upon

in tournament poker is to bluff at an empty side pot when
a third player is all-in. This is a bet which carries a huge
downside—it gives the all-in player a much greater chance of
surviving, since the bluffer, by definition, has nothing—and
no upside either, since there are no chips in the side pot. Of
all the unwritten rules in tournament poker, this is the one