Because it struck me as ironic that everything else is private, but "your ISP" still can track you. What exactly can they track? And what's the point of private browsing if you're not all that private after all?

It's just to keep stuff out of your browser history.

So I can take it at direct value when they say that nothing will be recorded on your hard disk?

It simply means that Firefox says your browsing can't be tracked using the browser.
History, site logins (in cookies) etc. can't be tracked.
For instance if you're cheating on your partner, (s)he will not be able to track find out using your browser history.
Theoretically the same goes on for authorities in case you use your browser for illegal activities. Though authorities have more advanced tools and more options to track you online.
Some data will most likely be recorded on your hard disk, since some data like logins is needed for using a site.
I assume it will be securely removed when exiting the browser session.
Not using your ISP's dns servers and using an encrypted connection, a vpn or a proxy helps to prevent your ISP from being able to track you.
In some cases other can though like the owner of a proxy server.
Anyone who has physical access to your computer can install all kinds of software to track your online activity's and log every keystroke you do.
In case of using someone elses computer, if you have access to USB ports on a computer you can use a Firefox version on a USB stick.
In that case the data is recorded on the stick and not on the hard disk.

Good post thanks. So for the most part, apart from being tracked by your ISP, I assume that whatever you visit through Private Browsing will have traces removed once you are out of it?

You want privacy? Use a proxy in the Cayman Islands to connect through another proxy in Tibet, assuming that you have already routed your connection through at least three russian ones.

...You forgot to add through Africa. They will NEVER look there.

To get my thread back on topic, let's assume an EMP nuke specifically designed to target only network proxies has been dropped, destroying this entire world of proxies
Next.

O_o that's where all teh scammerz live... don't want to go there

Maybe GOG could add proxy services...

I have a friend from Nigeria..so I always ask him why he looks Ethiopian. That, and if has had it with a giraffe.

But I only trust Peter :P

Think of the possibilities, 5.99/month for private without porn or 9.99 a month for private with porn

You really know how to sell a product :(

That is what Sony's PSP is for. =/ Except with the cost.