It can hardly be argued that it is not their responsibility. I didn't borrow the game, but bought it. Therefore I would like to be able to enjoy it even after it could be erased from my pc/mac.
At least, they could have stated on the website that the buyers were going to receive temporary download links. If I buy an application online, I will be able to download it from the original website anytime I want to do it, as I have a serial key. (I merely store the serial keys and never (!) download and store the apps on cd's/dvd's, as I can always do it)
I don't like this system of Amanita Design! Please, offer us normal download links that will last forever or provide keys for the game, which will unlock its full features.
Very very disappointing, as it has already been stipulated by previous posters....