Way back when I was just beginning to experiment with Linux back in the 90s I installed ZipSlack, which was a GUIless 100MB distro based on Slackware that ran from a folder on Windows. It was okay but I couldn't really do much with it and back then 100MB was a chunk of space, so i went to delete it. But i thought I would give it one last hurrah by deleting it from Linux. So I made use of the infamous rm -rf and sat there thinking "this is taking a long time"... then realised I had my Windows drive mounted as a sub folder and I was in the process of wiping my hard drive of everything!