Broken Smile

"Look for the girl with the broken smile" says Maroon 5 in their song 'She will be loved'. And i have always wondered, 'What does a broken smile look like?' and my meagre limits of experience and imagination have not been able to conjure up any image. And i imagine myself walking down some street, years later in unknown future, minding my own business, and suddenly i would spot a smiling girl, and Eureka! The song would come into my mind like a revelation and i would exclamate in the joy of discovery, "So, this is what a broken smile is!".
Ah, the joys of fantasy. Talk about romantic expectations! :)