Both on FB and IG, I see people posting themselves before 10y and now. I have no idea how this challenge started.
Could it be a way to collect a colossal amount of data, that could be used to train age-related algorithms (e.g. recognition, progression, ..)?
Forget about data privacy etc., think it technically..for example cleaning the data shouldn't be trivial... Moreover, every person posts it's own version, for example some write onto the images.
On the other hand, FB at least have these photographs of yours more or less, it just asks you to label them now. :)