It's not so much the possibility to forget your phone in a cab that worries me, it's the fact that people are using crappy low resolution phones in the first place to document many of their most important memories, and many times they use apps like instagram to degrade the quality even further. I for one am extremely thankful that most of my own life and my parents' before that is recorded on negatives. I can look at the prints (something I rarely do for my digital pics) and I can make new ones, or even scan them and with today's technology get even more quality out of them than was possible when they were originally made.
Unfortunately I learned the hard way how things can easily go wrong with digital when about 8 years ago I went to study abroad (some of the best years of my life) and made the bad decision to not only use a shitty p&s digital to record my memories but also lost all of these in a HD failure at the end of my stay a couple of years later. All I have left are a handful of web-sized files that were uploaded to a server for sharing. Nowadays of course I make rigorous backups, but I would guess most people don't. Still, even if I hadn't lost them I wish I would have recorded those years on film. As the years pass you treasure your memories more and more, and I can only imagine how people in 20 years will regret recording theirs with a crappy cellphone, not to mention future generations. I don't expect people to start buying film cameras really, but at the very least get a quality digital.