FF "Private Browsing" mode sux..

all the private browsing mode does is Sandbox the current browser session so that once you close/exit out of the browser everything will automagically be deleted and un-viewable/traceble etc etc

ie website's you visit, urlbar entry's ie: bigboobies.com and pr0n video's you may or maynot view.

your able to still login as your still able to get a session hash, it's stored in the sandbox and once you either logout or exit the browser session it will then get automagically self destructed.

the 3rd party stuff here is just the geo-location / analytics / and advertiser stuff that the owners run to remote keep tabs on the forums monthly performance quota.