Turns out that Adobe is collecting all of its customers' pictures into a machine learning training set.

This is opt-out, not opt-in so if you use Lightroom, for example, it defaults to adding all of your photos to the set.

If these are unpublished pictures, work-in-progress, etc. they'll still be analysed as soon as they're synced.

I've been using Lightroom to sync photos from my Windows desktop to my iPad. Now I need to reconsider that.