Amazon may have feared a lawsuit if they warned people and thus gave them a chance to hide their illegal copies, but I think that would have been better than the current agitation. What I don't understand is why Amazon isn't making more digital hay, so to speak. Digital books have a fundamental advantage over print: they can be easily and cheaply corrected if they're wrong. An article in the NY Times on how digital publishing is fundamentally different from print points this out.
What Amazon should be doing is working on ways to improve digital content. They should provide links for users to report formatting problems and other errors, send that feedback on to publishers, and build a mechanism for delivering a corrected copy of the book to anyone who bought a copy that was in lousy shape.
Paper beats digital in some way—no power needed, resale is easy, no hardware costs, can be loaned to others. Digital needs to show off what it can do—not just wireless delivery in seconds, but wireless redelivery when needed, no fuss no muss.
But no more stealth raids.