Why are there so many more upsets in hockey playoffs compared to other sports?

              I heard just prior to the Stanley Cup playoffs 2012 starting that something like 23 of 64 (68?) first round pairings over the last couple of years had resulted in a lower seed beating a higher seed.  Sometimes a drastically lower seed, like a #8, defeating a #1.   It happens very commonly.   Herewith three possible reasons why.

                Goaltending – if a goalie gets hot, and it happens, they can dominate every game.  It’s not like baseball, where a dominant pitcher can only go once every three or four games.  And if the lower-seeded team’s goalie is the one that gets hot, shots that normally go in end up not going in.

                Penalties – there are hardly any other sports (lacrosse is one, possibly) where a penalty results in a clear offensive advantage.   That’s what power plays do in hockey.  Just a couple of successful power plays by the lower-seeded team can win a game against the higher seed.

                Lucky bounce – hockey is fast-paced, and the element of chance sometimes plays a part.  A shot off the backboards that pops right in front of the net, a deflection off the skate of an opposing player, a rebound that skitters  just out of reach of the goalie’s glove – all happen, and provide scoring opportunities.