[tptacek]

I don't understand what you're trying to say. It sounds like you're saying, "sure, there's a totally obvious and simple way that people on Facebook can take and republish your pictures that Facebook can't do anything about, but did you also know that there's also this really convoluted way they could also do that, and Facebook could fix that?"

If you publish images to the public on Facebook, all bets are simply off. It is a bad idea for Facebook to give people the mistaken idea that any settings change on Facebook could ever take back anything posted to "Everyone" on the site.

[Terretta]

Not talking about "Everyone". Talking about, for example, your best friend. Then you turn out to be a Russian spy named Anna. Suddenly your friend, who didn't care to download your photos before, now does want to download them.

More to the point, talking about changing privacy settings, and having the change work, where work is not defined as "defeat tptacek" but "defeat casual users".

The logical conclusion to "It is a bad idea for Facebook to give people the mistaken idea that any settings change on Facebook could ever take back anything" is for Facebook to remove any ability to set privacy more restrictive, ever. I doubt that would be popular.

While "you can't take it back" may be technically correct, most photos aren't being downloaded to repost, merely viewed inline online. There's no reason a user changing privacy to be more restrictive shouldn't expect that change to apply going forward.