Al,
I know I am going to end up sounding like a perma-bull here, and I am not. And I know you know to beware of a perma-ANYTHING, and ZH is definitely perma-bear. Their interest is shaping EVERY story to make it seem the End Is Neigh!
That said, here I go stepping out of my depth:
1. I have no idea what Apple's trade promotion budget is (I've gotten very lazy about this stock), but it's probably small. Very small. I'd be surprised if they were footing the cost of this promotion. It'd eat up all their trade promotion budget AND have the added benefit of pissing off all their other retail partners.
2. Our family has experience dealing with Wal-Mart (PM me if you want deets) and it's highly likely that they, Wal-Mart, are eating most of the cost of this promotion. I wouldn't go so far as to say "all of it" because that is unusual; but the majority of the cost of the promotion is probably being absorbed by WM.
3. The price of the iPhone is not $199. It is not $189. And it sure as heck ain't $130. It's about $650. I have no idea what the ASP is on iPhone 5— nobody does, yet— but if history is any guide is about $650.
So, in the unlikely event that the companies are splitting the cost of the promotion it'd be about $30 each (again, this is highly unlikely— WM is likely absorbing the lion's share), and $30 off a $650 phone is NOT 30%, it's less than 5%.
I don't think this is as dire for margins as ZH would have us believe.
Also, I'd take issue with the idea that mobile computing is a fad. (Not saying AAPL will always rule this space. They won't. Saying mobile computing is not a fad. Just ask Dell or HP if it's a "fad")
Hope you're having a great weekend and I look forward to cheating off you next week!
(EDIT)