Amazon has dropped the price of the Xbox 360 Arcade console to $159, as noticed by CheapCollegeGamer. The retailer doesn't mention an end-date for the promotion, but the listing notes that the price isn't shown without clicking to add it to the cart "because [Amazon's] price on this item is lower than the manufacturer's suggested retail price." It's rare for consoles to go on sale without it being an official price drop.
We've followed up with Amazon and Microsoft to verify that the promotion is isolated to just Amazon and not indicative of a general price cut.
Update: It's back to $199. Curiouser and curiouser.