According to developers, Diablo 3 doesn't have elemental damage effects, with the exception of ice which chills/freezes. However the developers said that, because of this added effect, the cold damage is reduced, when compared with other elements. But I don't understand what this means. It's either
1) When calculating the actual damage, if the element type is ice than it's reduced (like multiplied by 0.8 for example)
2) When you find a weapon/gear piece with ice damage, the effect is lower (for example you could find normally weapons with 3-4 fire damage, but you only find weapons with 1-2 ice damage)
I think #1 makes more sense, and it would also work for skills. Do you have more information about this?