Ok. Well I think thats how it use when you use the plug on the powerbrick. I have the same problem. Even if the plugs are grounded I get little shocks or a funny sensation from the surface of the machine. I dunno if there is any way of fixing it but I use the cable extension and it goes away. Try for yourself and see if it helps. If not someone else here maybe able to help you.
I thought I was going nuts.. I only get the little shocks at certain locations. I always use the extension cable.
On my current MBP penryn, no shocks. But on my Powerbook, which died last December, I would constantly get shocked. Not until I took it apart because of a spill did it stop shocking me when I touched it. I think one of the grounding "bumpers" was not touching where it should have. I am telling you about my powerbook experience with shocking because it is very possible you have the same problem. Though I have no way of confirming this, nor do I believe Apple will do anything. Though it might help to take it in, and see if they can do anything. Maybe mention what I said above, to see if they will take it apart to make sure. Who knows. Also, as an fyi, I am that person that will get a static shock off anything, and constantly get shocked by my car when I get in it. Where my wife never gets shocked via the same car. I still get shocked by my car, but never by the new MBP.
I occasionally get "tingly" feelings from both sides of my 2.2ghz MBP that can take one by surprise and hope that everything is fine with it. They aren't really "shocks" but more "holding onto a low voltage"...
The small shocks and tingly feeling can be the result of poor grounding on the outlet. In some houses (usually older houses) some/all 3-pronged outlets have nothing connected to the grounding prong. Do you still get shocked when you are plugged into a different outlet in a different part of your house? How about in a different building? I never get shocked when I'm at home, but fortunately in my office (very old building) I have an external keyboard, mouse, and monitor!
Mmm...that must be what it is. I'm trying to remember if it happens at my house at all. I know it does at the place I work, with older wiring.