Anything's possible with a company the size of Apple. I still think they keep the supply low intentionally to keep the demand and free publicity high. They did this with the iPad 2. They didn't have any to sell in their own stores, yet they added Walmart, Target, Radio Shack, etc as retailers. And launched it in other countries around the world with the same shortages. Coincidence? I don't think so.
Supply of product low is intentional for publicity? Conspiracy theory.
What to know why supply is low? Because producing Apple's devices takes significant investment in the production lines. Like the article says, how many companies require building their devices to use a quarter million dollar laser to burn nearly invisible holes in them?
Wasn't there an early article with the iPhone 4 where the Foxconn head said they had to buy some sort of prototyping lathe or CNC machine for each line just for the product?
http://9to5mac.com/2010/09/10/foxconn-making-137000-iphone-4s-each-day/
What about that Liquidmetal stuff they played with? Sure they're not using it yet, but it's just another example of how likely they're using many odd tools in their production lines.
I have no idea how long it takes to make each part of an iPhone 4 or a Macbook Air, but if starting a production line costs that much money, it's no wonder they can't make them fast enough.
Buying more manufacturing tools isn't the solution, it's not like those are something you just call up Home Depot and ask for. They'll have to be built to order too.
Besides, once you have these many production lines up, what then? Sales are always higher in the beginning and then taper off. If you end up with too many unused lines, that's millions wasted in extra lasers and robots.
All Apple can do is start manufacturing early with the expected demand. Wait too long and the finished good depreciate. Start selling too early and too many backorders. I doubt any of us would actually fair better in balancing this out for a product cycle.