Somehow I think it's not ok to post pictures of your children on Facebook. Maybe, in hindsight, they don't want that once they're grown-ups. Then again, maybe that's just me thinking that
It's more like breaking out wallet snapshots at a party, handing them off to a middleman who scans and stores them for future analysis, then maybe shows them to your friends (with some advertisements mixed in) depending on whether or not their algorithm decides it's profitable to do so.
Personally, I use an adaptation of the "an unloaded gun doesn't exist" rule and think that once you put something on the Internet, anywhere on the Internet, it is accessible by everybody for ever.