There is a recent study by Alex Clark and Brenda Chawner, Enclosing the public domain: The restriction of public domain books in a digital environment, which examines the way in which New Zealand public domain texts are digitised and hosted online. I commend the article to you as it examines issues of significant importance in the current digital climate.
Of particular concern were two things that the paper found. Firstly, despite being in the public domain, only 3 out of 50 digitised texts were available without further restrictions. It should bother us that works that are public domain are being restricted by those that host digital copies of them. While undoubtedly there is labour and expense in producing digital copies of these works, this does not change the fact that such labour is essentially mechanical and unproductive, and so does not itself generate any new copyright. It is particularly troubling that some services that provide these kind of resources claim, erroneously, that the texts they provide are protected under copyright. This is blatantly false.
The second thing of note are the access restrictions, generally through 'browse wrap' agreements. Personally I think browse wrap is more legally dubious than click wrap agreements, which is dubious already. Given that none of these agreements are negotiable, that no-one reads them, and in the case of 'browse wrap' "agreement" is essentially passive, I would love to see this area of law change, but I think it unlikely. Most of the access restrictions are actively, sometimes aggressively, and more problematically technologically, attempting to restrict what you can do with public domain texts, beyond the provisions of copyright.
Essentially this is co-opting public domain and tying it up again. While I think it's right recognise that time and money is invested in bring public domain texts into digital formats for further use, I do not believe that this is the right model going forward for how to fund that work.
And let's not even talk about the moral wrongness of asserting copyright on critical editions of texts that are over a millenium old.