It is uncommon for anyone below the 1930's era to smile in a picture/portrait. If you look at many 1800's photographs, you will notice that they are in a more natural state than smiling. Think about it: most people just smile during a photo because it's a given, but sometimes people just aren't happy. So, the Mona was painted sometime in the 1500's/1600's right, then it's odd for her to be smiling. That's why it's such a phenomenon. But again... her smiling is odd to some researchers. It isn't a 100% happy smile. It has mixed feelings - sadness, worry, uncomfortable
