Autoimmunity
I have no friends.
Without much fuss, Twitter has taken another step to be more like Facebook – and added a photo-tagging feature. And in the best traditions of social networks, the privacy-diminisher is switched on by default. The tagging feature means anyone can identify someone in a photograph they post, unless you realise it's happening, log …
There's the set of all people, and the sub-set who are Twitter users. The screenshot seems to indicate that a specific Twitter user can "forbid" their identification in a posted picture. What is the nature of that ID? Is all tagging done exclusively by Twitter handle, or can one post a picture and tag it with a free-form name, nickname or description, e.g. "that smelly bloke who hangs around by the lavs on the way back from school"?
If it's somewhere in the latter categories, then there's no mechanism for opting out that's workable, as far as I can see.
Now, pictures identifying living people (as opposed to just featuring them) are definitely personal data within the meaning of the Data Protection Act, therefore anyone can require that Twitter disclose the personal data that it holds about them, with a Subject Access Request.
Hmm. Despite the fact that there is a Twitter UK Ltd at 100 New Bridge Street, London EC4V 6JA; Company No. 07653064, there seems to be no registration of a Data Controller with the Information Commissioner's Office. That doesn't seem right...