New technologies change what we can do. Sometimes they make what we want to do easier. After writing a book with a word processor, one wonders how it was ever done without one. Sometimes they make what someone else is doing easier–making it harder for us to prevent him from doing it. Enforcing copyright law became more difficult when photo typesetting made the cost of producing a pirate edition lower than the cost of the authorized edition it competed with, and more difficult again when inexpensive copying put the tools of piracy in the hands of any college professor in search of reading material for his students. As microphones and video cameras become smaller and cheaper, preventing other people from spying on me becomes harder.