Star ratings in the physical world

5-star graffiti stencil source

There clearly is appetite to transfer popular social concepts from the Web to the physical world:
Free 5-Star Graffiti
stencils for urban annotation. Source 

prototype v.2 

Electronic alternative developed by ubinote. Prototype v.2 with e-ink screen and Wifi connection.
Connect via QR code, NFC or Bluetooth LE. Get in touch if you’d like to run a trial.