[bigpooch]

Wasn't it Zadeh that mentioned quite plainly why drawing
four is sometimes weak?

In situtations where the BB is facing a possible draw (not
when the limper has called with position and drawn three:
it's rare to find a player that would just have two high
cards rather than a pair), you sometimes have to pay off
with a hand that beats a bust. When drawing four cards to
an ace, the top 5/9 of hands include not only 22, but also
AK high and they represent the calling hands when facing a
bet (after drawing four cards).

When the SB completes and draws three it may be just a draw
to some high cards so you can also call with the bluff
catching hands as above and if a player is willing to do so
after drawing four, that's fine. Now the bluff calling
frequency is 1/2 instead of 5/9 but in any case, 22 falls
within the top half of hands after drawing four.