Playing Devil's advocate, these watermarking increase the probability that innocent people will be convicted. Under the law, copyright infringement is not a strict liability tort, ie., one must be at least unreasonably negligent in allowing the work to be copied. But with this mechanism, if an ePub containing a watermark appears on a file sharing network, the buyer is always assumed to be the culprit.

As an example, imagine the user kept 24 books in a personal Dropbox account for easy reading across devices, and someone stole the account's credentials and released the books. The user is now on the hook for $200k in statutory damages despite being himself the victim of a crime instead of the perpetrator.