This seems like an excellent time to point out that storing a single copy of irreplaceable data like photos is a really bad idea.

I am certainly not undervaluing the consequences. Data loss is always huge, but I would say, comparatively, the likelihood of losing your data to this Windows bug pales in comparison to say, getting locked out of your Google Photos account and having no way to appeal. (I have a friend who is unable to get into a Google account with correspondence from a deceased family member.) I don't feel like Microsoft is even close to the industry worst in putting your data at risk because of this bug.

And with regards to the massive user base, bear in mind, this was caught in the very early stages of a slow, phased rollout process, explicitly for this sort of reason. So it was a small percentage of a very small rollout to begin with.