In researching IM, I've seen other gurus do similar things. They seem to do a big ass launch for a product, sell maybe 1000 units (or whatever) and then stop selling the product. Why?
Is this in response to piracy? Perhaps it's one method of battling the inevitable fact that eventually their material will make it onto the rapidshare sites, so better to create a huge launch and build anticipation and make a lot of money in the short run, rather than keeping the product for sale for the long run?
Also, buy "selling out" of the products (hard to imagine how you can 'sell out' of digital products) and updating the sales landing page to "Sorry! List control is no longer available, but go ahead and leave your email address and I'll notify you as soon as something is available in the future" allows them to:
a) build social proof (the product was so in demand that it actually sold out)
b) create even more urgency in the buyer (Dog gone it! It's sold out! I was ready to buy! Now I want it even more...)
c) build a list