Police shut links down, keeping it from the public who can help to find the culprits.. once the media disappears its only those voyeurs that will upload it again , so data harvesters can try to pull info from the source
Animal abuse videos are the worst since its even harder to find the source and since most value animals over humans those sources become lost due to reporting but think tanks like 4chan build to preserve the souce vids and allow vigilantes the time needed to analize the source