I have a beta of anonymous use. In this version you can choose what type of login you want to use, and it can be tracked via either anon (using IP address as key) or login. See the 'News' page for more info.
The code is actually smart enough to key your user setup by both, so for instance if I login via my notes name/password and customize it, it records my customizations by both my IP and username. So if I hit the site next time on the same PC without logging in, the system will find my customizations by IP, and display them without prompting for login.
The only downside is that someone could view/change my customizations if they knew my IP address and 'spoofed' it. Still, there's nothing really in there that's confidential, and anon is an option in the site config, so I see no harm in it.
See