The duel challenge in WoW is like the old-fashioned slap in the face with a glove, although often that's where the similarities end. Reading up on duels (the historical sort), I was surprised by the mechanisms in place to prevent cheating. Opponents have seconds who oversee the duel, choosing a field of honour and the exact rules, and refusing a duel is a mark of dishonour and disrespect.
In WoW, duels are easily avoided (though duel spammers who repeatedly challenge are quite annoying), and no honour is lost if you decline. However, some players have some strange ideas of what makes up a fair fight: using potions is generally seen as cheating (as well as a waste of potions), but what if the character is an alchemist? Does applying a leather armour kit to a chestpiece give a skinner the same advantage as a first aider applying bandages mid-combat?
It's an interesting question of where to draw the line, and having seconds might well help the cries of "Cheat! Cheat!" as well as cut down on the duel spam. Of course, there's little that can be done for those players who cry unfairness at a Priest using a heal in battle, but you can't win them all.