Free speech and fair use don't mean much if software end user license agreements, or EULAs, or website terms of service, or TOS, can take those rights away. Contract law allows private parties to agree to forgo most rights in exchange for some privilege. Vendors of goods and services take advantage of modern contracting tools, like click-through or shrink-wrap, to impose terms and conditions on using software or websites. These documents purport to limit the user's legal rights.

Two things have changed. First, it's no longer acceptable only to catch criminals during or after a crime has been committed. Counter-terrorism requires identifying and neutralizing threats ahead of time. Second, collecting information about everyone is now much cheaper and easier than it used to be. We spread information about ourselves as we use the internet, shop online, talk on our cell phones, send e-mail or use electricity. These activities leave a digital trail that database and search technology can store and access relatively inexpensively.