"I just bought a Samsung Series 7 (7100) 60" LED 3D HDTV and I had the same problem. Like "jameshoward1982", I discovered that when I Went to TV viewing and then into Menu -> Smart Features, 'Clear viewing history' is enabled. I was able to clear the 'Enjoyed Content' viewing history in one click for photos & videos. I hope this helps somebody (Samsung TV menus are clunky)."
I have a Samsung 60 inch SmartTV. I have used the USB input to watch videos successfully, and when removing the USB devise, thumbnail images remain on the Smart Hub as watched videos. Some of these thumbnail images are inappropriate for family viewing, but are still visible. If I reset the Smart Hub will this erase the video thumbnail images??