Here is a post from Maggie Stiefvater, author of the excellent Raven Boys quadrilogy and the even better Scorpio Races:
You should click through and read the whole thing, but here’s the summary: After seeing oddly poor ebook sales for the 3rd Raven Boys novel, she asked the publisher to not put out an e-ARC for the 4th and last. Then she flooded piracy sites with bogus ebook copies, which were badly screwed up.
Instantly all kinds of posts appeared by people who, to their dismay, had downloaded a pirated copy, found it was all screwed up, and had thus been forced (the horror!) to actually buy a copy from Amazon.
The persuasive conclusion: piracy crushed ebook sales of the third book so badly that the publisher cut the print run of the last book; the publisher thought that piracy was not the cause of reduced sales, but they were wrong; piracy was Very Bad News for Steifvater’s sales and seriously damaged her sales for the series, and would have done a lot more harm if she hadn’t pulled off this anti-piracy scam.
I imagine this is a bigger problem for more famous bestselling authors. But yeah. I got this link via The Passive Voice, where the Passive Guy has both comments and suggestions. I have to say, flooding piracy sites with tons of bogus copies does seem like a more useful strategy than trying to eliminate pirated copies. And I must admit, embedding viruses in the bogus copies has its attractions as well…