Don't like your bookmarks being stored in your profile folder? Want two or more users on the same computer to share a bookmarks file? Easy.
Using this method, not only can you share your bookmarks file with other Firefox users on the same computer (and possibly same network. I'm not sure.), but share the file with SeaMonkey users, or Mozilla Suite users, or Netscape users. If you share with SeaMonkey/Mozilla/Netscape, just remember that live bookmarks will not function.
If you have Netscape Communicator, you can even go as far as pointing it to your Communicator bookmark.htm file.
The \bookmarkbackups\ folder stays in the profile folder. The bookmarks.bak file travels with the bookmarks.html file.
Link: http://ilias.ca/blog/2006/04/customize-the-firefox-bookmarks-location/