There's a Firefox Add-on named "Facebook Container". Once you install that Facebook lives in a little box, Facebook cookies, Facebook whatever else, all trapped in the little box.

No effort needed, if you click your Facebook bookmark, or follow a link or whatever, the browser goes "Oh, this is Facebook" and traps it inside the box with the rest of Facebook without any extra steps from the user. There's a cute blue "Facebook" icon added to the URL bar so you can see it's working.

(I mean, or, stop using Facebook, but for many that isn't a reasonable option)

'We only use incognito mode for security. Since it's annoying to login constantly, everyone has dedicated machines that are powered 24/7 so you never have to shut down those incognito tabs.'

=)