Google seems to have realised this, finally:
I work on a project at Google called Google Accessible Search, which helps promote results that are more accessible to visually impaired users. Building on that work is today's release of accessible public domain works through Google Book Search. It's opening up hundreds of thousands of books to people who use adaptive technologies such as speech output, screen readers, and Braille displays.
As this notes, one of the advantages of opening up in this way is that the text may be re-purposed for adaptive technologies. Put another way, texts that remain closed, locked up behind DRM or similar, are largely denied to people who rely on those technologies - another reason why closing up knowledge in this way is ethically wrong.