I had a close shave shortly after I updated to Windows 10. The photos app, by default, cycles through photos on your hard drive as the background to it's icon. I don't store that many risky pictures on my computer, so I didn't worry about it at first, thinking that the algorithm just wasn't going through those folders. Imagine my utter panic when I'm showing my little sisters how to modify some settings on computers, and the background decides it needs to switch from some nice pictures I took at an airshow to something a bit more... mature. I don't think they registered what it was with how quickly I reacted, and as far as I know nothing ever came of it, but it certainly made me much more careful and thorough in finding possible mistakes.