Four states — Arkansas, Indiana, Nevada and Virginia — now have rules in place that force folks getting a driver's license photo not to smile. The "neutral face expression" allows the DMV to compare a new photo taken to those currently in the system. This helps avoid fraud using advanced facial recognition software.
However, Arkansas, Indiana and Nevada allow "slight smiles" because those don't interfere with the system. Just no huge, teeth-baring grins, it seems.
Twenty-seven other states use similar software, but they don't forbid smiling for the photos.