A smile can imply much. Just the right amount of lift at the edges can make you feel that a rascal is worthy of your trust. A large toothy one with one side of the mouth lifted becomes a lascivious leer, while just a hint of one, with a slight sigh, can make you think this soul has great spiritual depths.
In other words, a smile is a dangerous thing to depend upon, and I wouldn’t go leaving my lunch unattended because I trusted in one.