Firefox doesn't delete Sync data from the browser when logging out off the Sync server; option to be able to do that. And I doubt if the Portable version added that type of feature, as very few changes are made to the Portable Edition before making it "portable". At any rate Firefox Portable Edition isn't made by Mozilla, it is a 3rd party program that has permission to use the Firefox branding. Support for Firefox Portable Edition is over here: http://portableapps.com/forums/support/firefox_portable