As a software developer, you will know that high-aspiring programmers (like Joel) have a standard. He definitively said on a number of occasions “these are the ways we did not intend for you to play.”
For other software, depending on the ToS or the EULA, the developer may be obligated to fix an unintended use of their product. For instance, all my Adobe software includes a measure of “professional responsibility” on behalf of the developers, in exchange for our diligence as Creative Cloud Members. We report the bugs, they fix 'em.
The exploitation of a game system should necessitate a fix to an unintended game mechanism. I would think a more moderate view would ascribe less blame to the exploiter, with the big picture in mind.
As for the Dev PvP: a lot of the promotional footage from Launch and post-Launch are from epic team battles. It would not be a stretch, or a bad thing, to see them do this again. I got to see a few outtakes and it was supremely hilarious, in all the best ways.