Private Browsing Mode is for browsing without storing information on your computer. It has nothing to do with websites tracking you; that's what the Do Not Track feature is. We do require that add-ons respect Private Browsing Mode, and our privacy team is working on a recommendation (not a requirement) that add-ons also honor the user's Do Not Track preferences.
As the person who implemented Private Browsing describes:
Private Browsing aims to help you make sure that your web browsing activities don't leave any trace on your own computer. It is very important to note that Private Browsing is not a tool to keep you anonymous from websites or your ISP, or for example protect you from all kinds of spyware applications which use sophisticated techniques to intercept your online traffic. Private Browsing is only about making sure that Firefox doesn't store any data which can be used to trace your online activities, no more, no less.
As the person who implemented Private Browsing describes: Private Browsing aims to help you make sure that your web browsing activities don't leave any trace on your own computer. It is very important to note that Private Browsing is not a tool to keep you anonymous from websites or your ISP, or for example protect you from all kinds of spyware applications which use sophisticated techniques to intercept your online traffic. Private Browsing is only about making sure that Firefox doesn't store any data which can be used to trace your online activities, no more, no less.
http://ehsanakhgari.org/blog/2008-11-04/dont-leave-trace-pri...