[I work for Flickr]

Just as an FYI on our current plan for handling secrets (this has been a
very long process because it's very complicated):

Starting soon[1]:

* All newly uploaded photos will have separate secrets for original
sizes (but continue to have the same secret for the _s, _m, "standard"
and _b size (where appropriate).

* We will not change any secrets retroactively

* We will provide a way for users to generate new secrets for all their
original photos in a batch process

* There will be a way for users to change the secret(s) for individual
photos whenever they like (e.g., in case they see it posted somewhere
they don't want it showing up) and we may make this a checkbox option
when performing certain other actions (like replacing photos or making
them private)

* More info on how to handle this for API developers will be published
in advance of any changes to the API or the site UI

* Worth noting (to users, anway) that changing the secret on our servers
makes no difference if the original has already been downloaded -- if
it's ever been public in the past, someone could have done that

Good!

- Stewart

[1] Probably before the end of February.