I can understand their decision to stop selling print books, however, since they are still selling safari, why not continue to sell individual ebooks? Is the infrastructure and maintenance that much different?
This is surely the unspoken element of O'Reilly's change here, piracy of technical PDFs is rampant.
It only takes one person to "break" whatever protection there is on the content, its almost entirely irrelevant just how much protection is on that content, because only one person needs to go through the process.