The Privacy Policy of almost every company specifies that they identify the webpage you were visiting before you came to their site.
A very simple way to block this ability would be to do this: Everytime a Firefox user leaves one website to go to a new website, the Firefox browser takes the user to the Firefox homepage, and then on to the next site.
That way all the new organization would know is that the user was on the Firefox homepage before they visited their site.
Simple but effective.