I didn't do this today, but it was definitely stupid. In fact, it was not only stupid, it was STOOOOOPID!
Be warned, this is long. A little background first. I collect old commercials from between 1982 to 1999. I get some later ones, if I happen to like them. I find most of them on YouTube, and I've been doing this since 2006. I kept them all on a separate harddrive. Well, stupid me decided to break up the commercials from commercial blocks various people have posted (which was a pain in the neck at times, because, out of a group of commercials, they only had one I wanted). I had these in a separate folder on my desktop, along with folders of video files of various TV shows that I put in my iPhone. Well, stupid me moved all the folders to my external hard drive, and got a notice that said "Name of Folder already exists in this location. Would you like to overwrite it?" Me, being the idiot that I am, checked off "Yes to All," not realizing until it was too late, that I had deleted all but 50 or so of my 400+ commercials, most of which are no longer on YouTube. Basically 14 years of commercial hunting down the drain!
However, there's a happy ending to this story. I found a program that could recover them, and it actually worked, so I didn't lose those 400+ commercials after all.
Moral of the Story: WATCH WHAT YOU'RE DOING WHEN YOU COPY STUFF FROM YOUR DESKTOP TO YOUR EXTERNAL HARD DRIVE!