@tbrminsanity: How can you be certain that you developed a contact when you had a Charisma of 5, and not back when you were an ugly duckling dork in high school? You can't. You just have to accept some abstraction when you're dealing with character background.
@FastJack: Funny, I was thinking just the opposite.
In practice, Etiquette is mostly used for blending in and smoothing over gaffes, which are ephemeral things. I can see how it helps in making friends, but I wouldn't want to emphasize it too strongly. At the same time, I think all of the social skills have elements that are useful for building long-term relationships. (It doesn't need to be a friendly relationship either. Some people are loyal out of fear or lust.) I think some of them, like Instruction and Leadership, are even better reflective of long-term relationships than Etiquette is.
(Ninja'd! Faradon said it even better than I did.
And don't forget that Con includes Seduction, which you can definitely play into a relationship.)