Cloning iPads or iPod touches isn't illegal. This note from Apple iTunes Support tells you that you can sync 10 devices to one account per authorised computer. If you read here you can see that iBooks is somewhat different. As too iCloud. If you have a home account for the iOS devices in your home then you obviously sync to that account. Your child, brother, sister, aunt, dog, cat, husband or wife all do the same. This amounts to a lot of copying of data and contacts (Can you see how useful that is for school? Not so handy for family though. I'm not sure your 14 year old child would want his/her contacts syncing to your iOS device!) to many devices on the same account. Is there a limit? Well, yes and no. I point this out below too. The limit we find is about 20 restores. Then it becomes a little sticky and we have to use more than one Mac to finish completely. Hence, below you see we use 5. I am not using Windows PCs with iTunes as you can't sync multiple devices at once with iTunes on Windows. See below from the Apple discussions board.

The rest is over here​