I had this problem with a car charger I purchased at a gas station. Thought it was the chargers fault, but it still charges the phone, so I wasn't too concerned.
Yea, I've actually only used the charger with the laptop, just cuz i always have it out and on.
The biggest definable symptom is that when i tap something to select it, it will often thing I'm scrolling the screen. The next big one is when I touch the top of the screen, sometimes an icon on the bottom of the screen is selected. It's odd. Definitely not my imagination
on another an/droid forum (or earlier on this forum, not sure) - this very same question was raised, and it was (thought to be) traced to cheap power adapters. Some said it didn't happen with the stock adapter - (it happens with me with another micro adapter for my bluetooth handsfree dev.)
I can confirm that making the connection to the metal case stops the shake (on my phone). even with the other hand.
Just make sure that your usb port, aftermarket charger, etc. provides at least 500 milliAmps. The stock motorola charger provides 850 milliAmps. Unpowered USB hubs don't provide even 500, even if the USB port in the computer does, and not all do. The capacitive touch screen relys on the ability to detect capacitance changes, this requires a certain amount of power to be available. When you use an aftermarket charger or unpowered usb hub, you are not allowing the device to have the amount of power it needs to properly sense the capacitance changes on the screen.
Granted, they could have designed this differently, but that is the way it works.
This is not an issue that I have had customers voice. I will look into this further and see if I can duplicate this on a phone, I never had a problem with this on my Droid. But if I notice this, I will "send it up", as it were.