I've been giving some thought as to whether it's possible to be completely anonymous when connected to the 'net. Whilst I can think of obscure cases where it might be possible to track this setup, I reckon using the following list it would be next to impossible to track the user.
* Laptop with Wireless card
* bootable Linux Distro (preferrably from something like a Magazine cover disc purchased with cash). Use a different distro each time you boot.
* No persistant storage in the laptop at all (remove the hard disk)
* Change the MAC address of the Wireless and Wired Network cards on boot. Use a different one each time you boot.
* Find free wireless access, for this use something like the backnet nodes..
* use a decent gain antenna, so you can be further from the Wireless AP.
* Connect to the TOR network and direct all traffic through it.
* Don't put ANY personal information into any site
Now some of the steps there, eg, changing distro and using only magazine cover discs are only for the extremely extremely paranoid, but a basic version where you boot off the CD change the mac address connect over wireless and use TOR, would make it very difficult to tie up Internet activity to any real-world person....