Skin tone preferences change over time (think Victorian era - pale confined women were the fad
, I think.
I agree with Ccoa. These days too light of skin is considered unattractive as well (hence all the tanning booths, fake tanners, bronzers etc which really sucks for a very fair girl like me).
I don't think I have ever heard about dark being unattractive, but maybe it depends on where you live. I certainly have never heard someone complain about being too dark. One conclusion of beauty studies has been that averages = beautiful, perhaps the same applies to skin colour. (e.g. Halle Berry over Naomi Campbell or Cate Blanchett...)
I didn't word that very well, and I have no overall point, except for that while beauty standards set by society suck, I hope that many people will look past that after gettign to know someone. Despite that, I know few people without their own preferences for looks, race, etc. on some level.