I spent ten years as a system administrator. I've installed Internet filters, servers of all sorts, designed networks, installed firewalls, written programs, and have a working knowledge of IP addressing, subnet masking (discussing which will simply kill a party), spoofing, phishing, and cracking, and other stuff. If I've learned nothing else from all this, I've learned this:

If the authorities want to track you on-line, they can and will.

All you can do is make it difficult for them.

Take email and the "Patriot" Act. You go to the local public library to send a nasty email to child. The cops don't need to search the library's servers -- they can check the servers at the library's ISP, or the ISP's ISP's servers. And it's actually quite simple to determine who "owns" a block of IP addresses and to whom a particular one is assigned (with DHCP, at any given moment). If you use a ten-dot private IP address at home or work it still must to through a public address to connect to the Internet and the WWW.

Of course, the authorities have to have sufficient reason to go through the trouble.

And if you think that any firewall is gonna keep any government from cracking into your computer, guess again.

There's even software available to "cops" which can, in effect, "freeze" your OS and data so that it can be examined without changing or erasing it (although erased data can, if worth it, be retrieved as long as the hard drive isn't physically melted down).

The drives from the computers at the WTC, for instance, were taken to Switzerland for data recovery after the 9-11 destruction. And the data is being, slowly, retrieved.

But such things cost, sometimes very much. And as I say, it's gotta be worth it.