Filed under iphoto
I've got about 11k photos, and lots of them have faces of things like wax figures, or people I don't know in the background. I don't really care about those "people", and so I need to remove them.
It's actually really easy. Simply create a Smart Album (Option+Command+N), and select "Face", "is", "unnamed". Now, you can go through the list of photos, removing selected faces with ease.