Ah crap, just bought the MBP 13" and I have the electric shock issue, found this thread and used the long cable, it's fixed now.
How can a company like Apple can possible mess up like this?

They include the grounding on the extension but not on the short one? gosh.

no, i can confirm already, the plug head, oh god i dont know how to describe..
the plug head doesnt have the grounding metal to attach to the grounding metal outside.

while the longer, thicker's plug head has the metal to connect to the grounding metal.
i use that one, instant problem solved.

yea i understand but as a product that will sell globally why dont design an adapter that's suitable for each county's plug? i.e malaysia should have the grounding metal included because i believe almost all commonwealth countries are using the 3-pin plug design.

and, i've never been to US before and I wonder how their grounding system works, coz everything is just 2-pin there

Then where does the grounding current goes? Since there's only 2-pin, one is live and the other is neutral.