1. there is a dispute over ownership of the photos - copyrights or family
quarrels.
2. there is a question about the content of the image - somebody doing
something they shouldn't - embarrassing or illegal.
3. there is a question as to how the possessor obtained the photo in the
first place - i.e. something lifted from company files without due
authorization.
4. there are collectors who like art collectors and every other kind of
collector, revel in having a unique something that nobody else has.
I tend to break the collectors out as 2 different types. Those that collect
for the sake of owning something unique and. investors who collect in the
hope of what they collected will some day be valuable.
From my observations the investor types check-out before they can cash-in.