I'm not sure whether technological fixes to prevent copyright infringement are the way forward. Somebody who copies and distributes an unprotected pdf file is breaching copyright; it is hardly the ISPs fault that they have not made this physically impossible. More important is the moral argument: what rights we think we are buying when we pay for a download.
With music, the problem used to be that people considered that paying for a track or album in one format ought to give them the right to transfer it to other formats without having to pay again. This view had no legal basis.
Someone paying for a pdf might expect to be able to print it out a few times if they needed to for some reason, and save a backup copy on a second computer: locking off this sort of functionality would be bad, not good, for ebook publishing.
Commenting by HaloScan
