I thought the use of scarcity really drove the growth of this business.
I agree, but it may be more useful to discuss what else was done to enable the scarcity-driven growth to succeed. Most of the time, if you try to create artificial scarcity around a product, nobody is going to see it to know how much they want it.
What do you think are the critical conditions that need to be met before scarcity becomes a viable marketing strategy?