It's a terrible decision made by dropbox
that March 15, 2017 that resulted thousands of links to dropbox just flat out “vanish” because they decided to make these links private by default
If any user who post stuff on dropbox using the public links goes inactive, it is gone forever. It is sure as shit when they excluded the internet archive from saving links to the file
I think what happened is because of an accidental restoration of previously-deleted files
Got to be careful, I advise anyone to upload the same file in multiple places and have backup links. Last December (2018), tumblr's new TOS and reliance on automated detection to enforce this new TOS resulted many innocent images and posts
being wiped. Even tumblr's own announcement got hit.
Again, inactive users = content gone forever.
Give thanks to RPG hacker for working on Asar.