Apple planned and facilitated the long lines by purposefully not having pre-orders and in-store reservations and limiting initial availability. They wanted the news to report the "long lines" and "sell-outs" for publicity purposes. It takes a coordinated effort between Steve Jobs, Tim Cook, Phil Schiller and the operations and marketing teams at Apple to set up and execute properly. Make no mistake - they know exactly what they're doing. Many companies in the world are envious of their extraordinary ability in these areas of business.
This makes the product seem more desirable to certain types of people and is a well-planned marketing ploy to boost sales numbers in the long term. It also nets Apple a lot of media attention at ZERO cost to the company. It's damn near business genius.
How does not having sufficient stock lengthen the queues? Not allowing preorders could do have that effect, but how would people arriving early to buy one know there is insufficient stock? Launch hype can't do more than cause an initial blip in sales if the product doesn't have wider appeal. Thousands allegedly queued up to buy Zune 2.0, but that wasn't a lasting effect, so wait until next week.
I decided not to get an iPad 1.0 because Apple was bound to find issues with the first design in the wild that could be corrected easily. I'm not sure I would be the first to buy 2.0, but many others who made the same calculation would be keen to get one.
I'm sure that Apple would not deliberately constrain the supply to the extent being reported here. Some people are going to be pretty annoyed that they waited for hours and bought nothing.