In what may or may not be good news today from the Blizzard Store, it looks like the Blizzard Authenticator was back on sale for a short time. It sold out rather early, and there was some rockiness with some orders, but it looks like Blizzard's at least trying to get back on track in delivering this extra layer of account security. Unfortunately, although it was showing as purchasable just an hour ago, it once again shows up as Sold Out currently.
There's no word yet on whether they've fixed any problems with keeping the Authenticator in stock, so it may be that they simply got in one shipment and are waiting for another. Hopefully, that shipment comes soon and they can work out their stocking problems a little more permanently. Until then, I'd sit tight and wait a bit. At the least, you don't want to be like the poor folks tipster Aaron pointed out to us, who are bidding up to $93.00 for one on eBay.
Thanks to everyone who sent us a heads up on this!