Individuals will not be linked properly and creating new links between Personas will not work.
The configured primary PersonaStore's backend may not be installed.
If you are unsure, check with your distribution.
Just be sure to set your default address book storage by opening the AddressBook gnome application, choosing something like "Local..." and hit save. After that the annoying warning goes away from ~/.xsession-errors
If like me you're awfully annoyed by the new feature in Firefox version 13 that when opening a new tab shows thumbnails from your browsing history, do not despair. This is how you can make that a lot more useful by either setting it back to blank, or your favorite URL:
in the URL type about:config
promise that you will be careful
search for about:newtab
double-click on the entry to modify it
set it to about:blank or your favorite URL like kiskeyix.org
Perhaps one day this feature will be more useful and you might like to reset this setting back to its default, but at the moment is simply uselessly annoying.
I get from this blog post (and this update) that about 6.5 million LinkedIn accounts were posted online and the passwords were simply hash'd without using a salt. Judging by this, it's perhaps time to close LinkedIn altogether as not knowing that passwords need to be encrypted and not simply hash'd seems to me like a sign of how weak their infrastructure is.