Many stores already do this without telling customers. There's a reason women return clothing they tried on at the store after getting home and seeing it in their own mirror. There was even a chick on shark tank selling skinny mirrors (but she was a ham and she was doing it to make other hams feel better about themselves. She got shut down for being a dishonest POS). I have seen them in hotels too. I can tell right away because my face looks too long and thin. Very strange.