Too many threats of mass deletions that would effect other posters.
While its all well and good that someone may want to delete "their threads" as an act of vengeance, the system forces ALL posts in the thread to be deleted at the same time when Post #1 is deleted.
The if you started a thread that has a couple hundred replies in it, and you delete your thread, you will also trigger the deletion of every other post in that thread.
Its bad enough when someone starts deleting their own posts in a thread, which tends to destroy the readability and continuity of the discussion, but its even worse when they assume ownership of everyone else's posts and delete them as well.
So we placed a 2 week limit on Self-Editing to preserve the integrity of the threads on the site.