the answer is....
YES.
Blizzard considers that when you step into a PvP zone you will get a warning message. They feel if you continue beyond that point you are making a conscious decision to be at risk of death.
So, people who say you cannot PK, are technically wrong....you CAN PK other people once they have entered the zone.
I am referring to the true definition of Player Killing in the sense that, you attack someone unaware of your approach and kill them not so much looking for a fight as much as attempting to commit 'murder'.
Of course, all PvP starts out with players attacking someone else first, but typically, it's less swift and stealthy and more confrontational (toe to toe).
Source: I asked this same question of Blizzard staffer, Alan, at E3 personally.
