When I read this today, at first I couldn't believe it, but when I checked it, I found the info to be true. On jailbroken devices, iBooks will throw an error and tell you to reset your iPad if you try to open an eBook for reading. The background is that iBooks will try to load an unsigned app. If this works, it know that your iOS-device is jailbroken. Now... if Apple does this with other apps as well, i.e. Calendard, Safari, etc., we're really in for some problems. Interestingly, I found that this only seems to occur if you try to open an eBook that was purchased from Apple's bookstore. Third party eBooks downloaded to the iPad via iTunes will still open just fine. As I have 90% eBooks from external sources (legally acquired, mostly ePub), I'm not really affected by this right now. I'll simply stop buying eBooks through Apple. Could someone try to verify this? I wonder why this happens. Any ideas somebody?