[thejeff]

At some point, pretty much anything you do, unless you're really in contention for winning yourself, is kingmaking.

If I help take down the leader, that's likely to throw the game to the next most powerful. If I don't, that leaves the leader winning.
Obviously this only really applies when the end is near. Taking an early leader down still leaves the field wide open.

If you're just talking about last gems and items when you're beaten, that seems a small part of kingmaking. I'd be more likely to give stuff to a surviving ally than to just a random enemy of my enemy.