Like many users, I use Xmarks to sync all my bookmarks. If I lose it, anyone who runs my FF portable will be able to visit all my saved websites, and be logged in as me.
I don't have admin rights, so can't use TrueCrypt to protect the drive.
I use SanDisk 'Secure Access' for office documents. But encryption doesn't work well for the portable apps folder; it takes too long to encrypt/decrypt, and the apps don't run from within the container, so you have to then copy everything out and back in.
How does everyone else secure their portable firefox?
The only way you can run something from within an encrypted software drive is with admin rights and by using something like TrueCrypt or FreeOTFE. Without admin rights or without having TrueCrypt pre-installed on every PC you use, you CAN NOT use an encrypted software container to run apps from.
Sandisk's Secure Access software is basically the equivalent of using 7-Zip Portable and adding all your files to an encrypted/password protected 7z files when you are done with your drive and extracting them all when you plug your drive in and want to work with your files. That's why it takes so long. If you just packaged up the Firefox profile, it would take a little less time.
If you want a truly secure and encrypted container you can use everywhere, you need a hardware encrypted drive like the PortableApps.com Carbide. It requires no admin rights and all your apps and data are secured with AES-256 encryption.
Sometimes, the impossible can become possible, if you're awesome!