I frequently smile, nod, and maybe say hello. Especially when I was working at a large company. Some people do not want that contact. I never felt slighted if the response was "private". I would say it depends on how well you know the person, sometime it works, sometimes not.

I guess if one is looking for acknowledgement of self worth it can be a bigger blow to that if we interpret it as "not the freshest flavour in town". If one is comfortable with one's warty personna then it does find a happier balance. Heaven knows I have been low enough for it to matter in the past.