You make it sound like Apple is the only company with the resources to do it right. Remember, there are many other multibillion dollar companies with deep pockets. Don't feel like Apple is cheating because they are successful.
They have the clout in the market to do it. Others do it to (Sony, Microsoft). It very logical, in that making something appear as a scarce item will increase demand for it. For example, if the news said that gas supplies were very limited to unavailable for the next two weeks, within an hour there would be lines at the gas station and police in riot gear. Apple will plant this idea in the minds of consumers and when they do see one in the next week or so, they will think "oooh its my lucky day" and buy one.
I don't think Apple has a huge storehouse of new iPads they are sitting on thought. I think its just that they limited the initial run and will scale up from here.
I might be jaded after they changed the the whole pre-order and in-store reservation system to make lining up on launch day a necessity and not an option.