Don't Smile?

A study from Michigan State University reported that customer service employees who fake smile throughout the day end up with a worse mood and withdraw from work, which affects productivity. But if the same workers focus on something positive, such as a recent vacation, it genuinely affects their mood and they withdraw less. Read the article here: MSU Smile StudyWhat do you think of this study?  My feeling is, as a customer, I'd rather encounter a smiling customer service employee whether they felt like it or not.  And furthermore, if I'm at work but I'm thinking of my last vacation, that suggests that I don't really want to be at work.  I'm just saying..