What makes a photograph worth keeping?

"You want pictures of the little darlings taken on their birthdays, pictures when they first put on long pants, pictures in their new suits. Those sort of pictures clutter up the house and don't mean a blessed thing."
"They mean a lot to Arthur and me," Mrs. Gentrie said.
"Well, they mean nothing to me. They simply are a waste of good photographic material. You find family albums filled up with that sort of junk." She turned to Lieutenant Tragg and said, "What I want are pictures of unusual cloud effects, of trees against the sky, of flowers. I could win prizes if I just had enough money to get myself a car and didn't always have to use photographic material which had expired."
-- The Case of the Empty Tin, by Erle Stanley Gardner (Pocket Books, 1949, p. 137-138)

I am getting a big kick out of this Perry Mason story. Here I am, a lady who takes a lot of photographs of clouds, trees against the sky and flowers. Did I mention that I take pictures of flowers? No, I am not interested in making any kind of money out of taking pictures. I just do it for self-expression. But ...

I appreciate those pictures my ancestors took of their children over the years. I am converting all the albums to digital, although I keep the originals. But no albums for them. Storage boxes for the ones I will keep and an effort to get others to people I think should have them. One relative called me the family archivist and I am comfortable with that. And nothing makes me happier than finding yet another batch of old, old photos.