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?