There is an additional problem that a license change may legitimately be a correction rather than malfeasance.  It's not the world's most common problem, but I have seen several instances where a Flicker user copied a CC-SA or CC-NC work from someone else but mis-stated the license as PD or CC-BY, etc.
In a couple cases where it has happened with my own works, I've contacted the Flickr user to get a correction.
This goes to the general question of how much are you willing to rely on the accuracy of statements made by largely anonymous people on the internet, really?  And do you really want to be in the business of assuming that their first statement was more correct than their current one.
Personally, if you can't establish authorship more specifically than an online screenname, I'm inclined to favor deleting images when things like ambiguous/contradictory licensing claims come up.
Also, it's worth noting that even if you have ironclad documentation that a legitimate license had been communicated, that only addresses that you were acting in good faith.  Good faith actions eliminate the possibility for punitive damages, but if you rely on a license declaration that is incorrect (for example because the Flickr user stole it from someone else), you are still potentially liable for actual and/or statutory damages.  Which is why professional publishers usually expect a clearer chain of authorship to avoid getting duped.
-Robert Rohde

On Sun, Mar 30, 2008 at 3:42 PM, Platonides <> wrote:
David Gerard wrote:
> checkuser-l is chasing cross-wiki vandals. Problems we've noticed:
> 1. Flickr review just checks whether an image is marked on Flickr as
> cc-by or cc-by-sa.
> 2. There's no protection against someone changing the licensing.
> The actual threat model is someone bringing a case of copyright
> infringement. Would screenshots of the licence as was be enough for
> 2.?
> - d.

It's a flickr problem on not preserving logs for license changes.
We're flickr reviewing to be sure if that image was free or not. So it
can be reviewed either by
a) The bot
b) An admin or trusted user (and it is in checked that the template was
set by a trusted user).

Both of which are trustable. If any of them would be willing to trick
the system, they could easily fake a screenshot as well.

Also, we have no way of dealing with people uploading copyvios to
flickr, then taking here with flickr as source (other than manual

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