NHL reseeds. The other sports don't, although the NFL has divisional matchups based on who won in the wild card round, USUALLY focused on keeping division foes from meeting, if possible.
2 schools of thought:
1. Reseeding isn't fair to the team that beat a higher seeded team, and the winning team should now go into the shoes of the higher seed since they earned it. The problem with this theory is that it ignores reasons why the lower seed won -- injuries to key players, etc. The other problem is that another lower seed benefits by having to play, say, the 8th seed instead of the top seed in the second (or later) round.
2. Reseeding makes the regular season mean more, and in series like basketball, hockey, and baseball, isn't what we are after is finding the best overall team? The problem with this theory is that you can only reseed to an extent -- in the NBA, for example, reseeding would only be done by conference and if the 2 best teams in the NBA are in one conference or another, that's too bad -- but it largely defeats the purpose.
I keep going back and forth on this. If Memphis wins tonight, you have a 4/8 series, and a 2/3 series. Memphis would deserve a big break for beating the Spurs, but don't the Lakers and Dallas deserve something for having a better regular season and (probably) being a better overall team?
If the NBA would ignore the East/West divisional playoffs and just go to a 16 team tournament (even IF you left in 8 teams from the East and 8 from the West), then reseeding would make a little more sense. Otherwise, leave it alone. For the most part, it works out OK.