host it yourself? (Score 4, Informative)

From the debugging logs, it seems like the information is just stored on a server via HTTPS+WebDAV. So if you control a web site (and you trust it more than you trust Mozilla), just change the Server Location (in Advanced Settings) from "https://services.mozilla.com/" to your own server. You will have to create a directory underneath that is the sha1sum of your account name, and it is up to you to set the permissions on the directory properly so that no one else can access it. Of course, this is all just an educated guess, but... "The rest is left as an exercise to the reader." :)