I have the same problem. There is some very strange corruption going on here. After creating the Smart Album with Faces = unnamed, a few were found and the face boxes deleted. However selecting all my photos (I exported a small event with 367 photos to a new iphoto library) and getting info, it says I also now have the faces I have added before PLUS 110 unnamed. Going to any photo with this issue does not show any such unnamed selection boxes! If I add a box and try to delete that single box, iPhoto deletes ALL the faces associated with that photo. Then it grays out Add a face..!