Five years ago, during our research on link previews, we discovered that Meta servers download every shared file in Facebook Messenger and Instagram DM in full鈥攅ven if it鈥檚 gigabytes in size. Now, looking back, it would be interesting to know if Meta used these files to train their AI models. Meta insisted it wasn鈥檛 a bug. When we published videos demonstrating the issue, they asked YouTube to take them down. YouTube removed one video and gave us a strike.