Simple, the demand is more than supply, in most country. However, in some countries there are cases of lesser demand due to the affordability. I heard (not confirmed) that in KL the D3 is not selling as fast and you can grab one at lower than Singapore price (no warranty though).
Also heard from friends in China that their Xin Hua(not sure of spelling) national news agency had bought and took delivery of more than 300pcs of D3 and accessories including lenses in preparation for the Bejing Olympic.
If you look into the demand in the US and Europe, it overwhelms our tiny little red dot's demand.
If all these are true, why it is not easy to understand the shortage.