This kind of reminder can happen even if the person isn't on Facebook. Every few months, a "Hey, remember this from 5 years ago?" photo pops up with a now-deceased friend of mine. It's depressing, and my effort to get Facebook to stop showing me "Do you want to share this memory?" photos has failed. She wasn't even on Facebook. I suppose I could go through all my old photos and delete them, but I'd prefer not to be prompted at all.