I can't speak for Flickr, but I can tell you that one of their larger competitors simply does a logical delete. That seems to take care of any legal obligation.

I can't speak for Flickr, but I can tell you that one of their larger competitors simply does a logical delete. That seems to take care of any legal obligation. I should note that this not true in the case of child porn. Once the feds give them the signal that is completely purged.