Here's a 5xp RFE for you! This was a feature in MozClassic (the code that was gonna be Netscape 5 and was based on the communicator codebase but was scrapped late 1998). I noticed in the Window > Privacy Tools menu (the equiv of Tasks > Privacy and Security in the rewritten moz) there's an 'Anonymous Mode' option in the menu. In the 'Understanding Privacy' (see URL field for link) document it details what this feature does: By clicking on a menu item, you can chose to become anonymous and then later you can become yourself again. When you become anonymous, all cookies on your hard disk are temporarily moved out of the way and a new list of cookies is started. Any cookies that are set while you are in this anonymous mode will be put in this new list. Later, when you become yourself again, the new list is discarded, and your original cookies are restored. So whatever tracking the site was doing while you were anonymous is related to the anonymous person that you became and not associated with the real you. The browser goes one step further when you become anonymous and refuses to tell the next site you visit the location of the site that you just came from. After all, it was the real you at that previous site and you don't want that information associated with the anonymous you. For the same reason, the location of the site you just came from is not divulged to the first site you visit after you become the real you again. Note that you are not giving out any more or less information (other than occasional lapses in where you came from) when you visit a site anonymously than when you visit it normally. It's just that whatever information the site records about the visit (cookies), it does so for a different person.

See also bug 155300, guest profiles.

do we want this? other than being a "gee whiz, this is neat!" feature, how useful would this really be to users?

If a user understands what privacy mode does, he also understands how to create a new profile :)

marking WONTFIX. Create a new profile if you want to use a different set of cookies. If someone can come up with a really really good reason for implementing this, go ahead and make the point, but a new profile does the exact same thing at zero cost in codesize.

V per comments. I don't 5xp.