Smiling considered a sign of stupidity?

I believe that smiling, especially at strangers, is seen as a sign of stupidity in some cultures. I'm not sure if this belief is limited to culture alone. I used to smile at people a lot and a lot of people gave me the bimbo treatment. When I don't smile, I've been told that I look unfriendly! I'm not much of a smiler anymore and I'm pretty comfortable this way. I don't believe that a person has to smile to have good intentions, be friendly or kind. You just can't win with people so why not do what makes me comfortable? If I smile then I'm considered approachable/accessible yet stupid and if I don't smile I will seem snobby/inaccessible but intelligent? Then you get the people who give you that condescending "Smile! Why don't you smile?" crap. I only smile when it comes naturally. This is why I don't like to smile for pictures, that is unless the smile is spontaneous. I hate my smile anyway...so it actually pays to look serious.