It's possible Humble Bundle may have put watermarks to trace the files in case they end up on piracy sites.
In my opinion, I find HB's business model reasonable. It trusts users to be willing to pay a bit of money to get the books. It is also upfront about where the money from the sale goes (to itself and various organisations) and even allows you to adjust the amount each one gets.
By trusting users in this way, it hopes that users do not abuse the trust by giving away the books to piracy sites. Instead, I believe it hopes to encourage more people to come to the site and pay for the books (and support organisations), rather than free-load the books via piracy.
This is, of course, just my opinion. But I have bought a few Humble Bundles and intend to continue supporting it.
In my opinion, I find HB's business model reasonable. It trusts users to be willing to pay a bit of money to get the books. It is also upfront about where the money from the sale goes (to itself and various organisations) and even allows you to adjust the amount each one gets.
By trusting users in this way, it hopes that users do not abuse the trust by giving away the books to piracy sites. Instead, I believe it hopes to encourage more people to come to the site and pay for the books (and support organisations), rather than free-load the books via piracy.
This is, of course, just my opinion. But I have bought a few Humble Bundles and intend to continue supporting it.