This reminds me of issues with Groupon, LivingSocial, and other kinds of online middle men for businesses selling discounted goods and services. When a business signs up with Groupon to promote themselves by offering these discounts, it sometimes leads to the business being overwhelmed with customers if they sell too many deals, primarily if the business provides one on one services. So, if a massage salon oversells their deal, they might have only a couple of masseuses booking thousands of massages - they might never be able to fulfill their obligations and might even go out of business because they can't book full price clients.

But if the business is one to many - say, a yoga class, a gym membership, a foreign language class - they usually can squeeze more bodies into the rooms and make it work.

And if the business is scalable - an online yoga class, an online language class, something you can download - you could.probably sell an infinite amount of deals and be just fine. The infinitely available deals probably won't crowd out the full price clients because they are likely not looking for deals in Groupon, etc. And you will garner future continuing / full price clients because the deal allowed you to sample their product/service.

ETA: I have hundreds of free downloads of books from Amazon, offered as promotions to introduce me to different authors/series. If I share these free downloads, is it piracy?