I wonder if with this rule "kill healing" would be feasible like in some team online shooter games.
In those games the medic sometimes kills a badly wounded teammate and then revive him because that uses less energy than to heal him.
In D&D that means that someone high level/HP whos current HP are below 10 is killed by the team and now has 2 turns to roll a 20 to heal 1/4 of his HP for free before the party stabilizes him and heals him normally (maybe just 1 point to kill him again for another chance of a free 25% healing).
But depending on how healing works in 4E this might not be necessary as the PCs might be able to heal up after every combat automatically. Still, in 3E using this rules it seems like a good strategy to save some cure serious wounds spells.