First and most importantly, memory cards aren't ideal for long-term storage of your photos. They're small, easily lost and/or stolen and are more fragile than, say, an external hard drive. If you DO choose to use them as long-term storage and they are the ONLY place you have your photos, then by all means, store them some place secure, like an in-home fire-proof safe or in a bank deposit box. Carrying around and traveling with your entire photo collection of your first born baby in your camera bag is a disaster waiting to happen. And in this couple's case, DID happen.
Second, and I've written about it before, your photos need to be backed up in several locations. For instance, an external hard drive at home, an external hard drive at a friend or neighbor's home, prints of your 5-star photos and somewhere in the cloud. This means that if your hard drive crashes or your house burns down, you'll always have another copy of your photos accessible elsewhere. All too often, when disaster strikes, we see on the news that the main possession people come back to find are their photos and the memories and comfort they provide.
Third, so many of us harbor stress and anxiety around losing our photos, yet don't take the proper steps to back them up. It's not rocket science and does take a little effort, but once you have a solid back-up system in place, you can rest easy knowing that you'll never lose all those precious memories. And removing even one source of stress in our lives can make a HUGE difference!