Stacking Glasses: Face Up or Face Down?

I'm not sure stacking your glassware face up or face down says anything about your outlook on life (like the proverbial glass half empty or full) but I am curious which you consider to be normal.

I always stacked my glasses facing up, primarily because I had never thought about it but also because when you take a glass out of the cupboard with juice in hand, you can simply pour and sip in one swoop.

Recently, it occurred to me that most if not all restaurants favor stacking their glassware face down. When I made that connection I decided to convert. I assume they know best since they are in the business of serving and preparing food.

So my question is, is it a cleanliness issue? Or aesthetics? And which do you favor?

(Image: Leela Cyd Ross)