I can pick my great-grandmother out of this picture - but who are the rest of these women? Relatives? A church group? Who knows...
You know who the people are when you take the picture and it seems like a silly thing to do, but it's worth it to take the time to label them. Even looking back through pictures from my childhood (and I'm only 32), I can't always remember people's names - people I thought I would never forget!
Also, if you have older relatives with fading photographs, take the time to sit with them and write names/dates/places on the backs of the pictures. Otherwise, this family history will be lost. When you have a box full of old pictures and you have no idea who they are, it doesn't make them quite as meaningful as knowing that it's your great-great-great grandfather and his brothers for example.
I have a huge stack of pictures from my grandfather and about 99% of them are not labeled. I know that they are relations - mostly his siblings, but I don't know who or when or where. :(