"As noted above, the nasty part of this image tagging is that it does not require participation or consent of the people who are tagged. Nor is there a mechanism to notify those people."
AIUI (and IIRC from when I actively used the site and even had 'friends'*), Facebook's logic is that "tagging" is when the name applied to a face in a photograph is linked to a Facebook account - and it's that which Facebook's opt out setting applies to.
However, it's still possible to apply a name to someone in a photo; there's no opting out of that because it's not linked to an account. So if your name is a common one, such as John Smith, being named isn't going to matter a huge amount - but if your name is less common, such as Thelonius Davenport, then even being named in a photo is a bit off.
"I'm not clear whether this actually removes your data from Facebook's facial recognition database"
Here's a more interesting question: Back when I actually used the site, with the notification option came the ability to disapprove a tag, which degraded it from being a linked tag to just a name. In that scenario, was the link still present for photo recognition purposes?
* That original account was deleted. These days, I have another account (set up as a test) but haven't added anyone as friends, and basically don't bother logging in. And Facebook's cookies don't persist beyond the browsing session on my systems.