I wrote a thing about how your favourites are public and searchable with not opt-out on HN: https://news.ycombinator.com/item?id=5756487.

Other than that, Flickr is one of the most privacy-conscientious services I know—which is why it took me by surprise that there weren’t controls for my favourites.

Flickr’s (general) emphasis on privacy and ownership rights are their main features to me. Maybe those are just hold-overs from the early days when monetizing your users’ data weren’t in vogue, though.