Correct me if I'm wrong, but most of the people I know of that use dual SIM cards use them because they're in many different areas with different providers in a short distance... so probably European mainly. But only people that are going to be doing that very often would really want to spring for that, I guess.

I worked in cell phone gaming for a few years and I know I never saw a single dual SIM slot phone in the over 500 phones we had in inventory. I think there's just not enough demand for it.