Many people have the custom of social kissing as a form of greeting people of the opposite sex. Is this OK? What about Issurei Arayos... Halachos forbidding physical contact between the sexes.
Can we judge appropriate behavior by observing what people - including many Orthodox Rabbis - commonly do?
Someone suggested that they see the argument inheres in what the masses are doing, not in a she'eilah to the rav. But that said kissing and chibah (sexualy oriented contact) are not so separable. Sure, when it's your great aunt Sally. But what if it's her grandchild, your physically attractive second cousin?
Here is my response:
What the masses are doing is directly connected to the concept of Derch Chiba (sexually oriented behavior). In cultures where this is common practice, it is less likely that doing things like this are B'Derech Chiba.
Physical attraction is highly subjective. The concept of Derech Chiba is based on that. If someone is attracted to a member of the opposite sex then, IMHO it would be problematic to claim that a social kiss is not B'Derech chiba. I say problematic because even in such circumstances it might not be Derech Chiba if this is the standard practice in a given community.
But if one is not attracted and it is just a social norm, then it is highly unlikely that it is B'Derech Chiba at all. So in your example it doesn't matter how young or attractive she might be. It only matters how you perceive her.
I think this is what the Gemarah means by saying that it is Assur to derive pleasure by even looking at the little finger of a woman. It is about pleasure derived, not the actual looking at a little finger. It is about one's own subjective thought and/or purpose in looking at that finger and deriving some sort of sexual stimulus by looking at it. If the act of looking at a little finger alone were Assur, then certainly looking at a woman's face should be. And we know that is not Assur to look at a woman's face at all... unless we derive 'pleasure' from it - pleasure in the sexual sense.
This is how I understand the concept of Derech Chiba. It's all subjective and social norms play a big part in that.