Why isn't God mentioned in Esther?

As you may know, God is never mentioned in the book of Esther, either by name (Yahweh), title (Adonai), or being (El). Neither is prayer. Why not? I realize this is rather open ended, so I'll try to give some objective criteria: 1. If it never mentions God, why is it in the canon? 2. What is the theological application to be gained from Esther *given* the lack of any reference to God. 3. *[waves hands](http://www.catb.org/jargon/html/H/handwave.html)* I have a few thoughts on this myself, but i'll try to hold them until I can get a good sampling of answers. (also, why hasn't this been asked yet? Have I missed an obvious duplicate? Or stumbled into the Area51 of ✝.SE?)