There is nothing stopping user from posting the file on megaupload (oops) another file sharing service as well.
Any protection, including DRM, link obfuscation or IP filtering, makes user's life harder. If they want to post it, they will post it. But once you started the war with a customer by putting those little obstacles in their way, you can't stop it.
Imagine a different scenario, where it's easy not to pay but you only have to deal with your conscience.
There are million cases when you can pirate easily but it's more fun to pay. Because you respect the artist or want to support the cause. I guess this is exactly the use case for Gumroad that I see.
i understand your ethical argument, but i still fail to see the practical usefulness.
easy beats free. piracy/copyright infringement means free.
you want to get people pay for something - you can't do this by optimizing the payment method. who really gives a crap about that outside of the techies who build that stuff?
example:
first one to make tv episodes globally simultaneously available, with local ads embedded or whatever will win over piracy. just look at the most popular torrents on pirate bay, etc - how i met your mother, etc.
itunes (as an example, same goes for netflix, hulu, amazon,...) is broken in that regards. non-us credit card and/or IP address? you're fucked. welcome to being a third-rate customer. well, fuck you then, pirate bay it is. movies, series, even apps are being restricted. even though the fucking majority of people (consumer!!) live outside the US.
So your first user buys the link. Say to a mp3 or a pdf. Now has the link in plain text.
What's stopping the user from posting that very link all over twitter, facebook, etc? "omg check out kanye's new single!1!!"
Seriously at a loss on how this will work in real life, with real customers.