If a scanned book appears online for pirate download, it's no wonder: someone who had a hard copy just scanned every page.
But there are a lot of PDFs out there that look like official publisher's copy that was never supposed get out of the publishing house. How does this massive centralized nature of book piracy happen?
I assume that scientific books that get published online as PDF ebooks may have been "contributed" to a file-sharing database, but other books, in print-layout are more difficult to get access to in large numbers.
Is something in the publishing chain compromised..? Is it probable that publishers' computers were intentionally infected with viruses for this purpose?