1. How do you stop people copying it or lending it to others?

2. How do you stop people printing it out and selling printed copies? (bear in mind someone already xeroxed the printed one and tried to sell cheap copies a few years ago.)

3. How do people carry it around with them?

4. How do people write on it?

Think about the answers to all the above before answering any of them. This has been talked through many times.