How to Test Stability of your USB Connections?
Look in:

Apple Menu > About this Mac

Then click "System Report" button

From USB in the sidebar you can see for each device "current available" and "current required" if you plug in a device and it needs more than 500MA then it need an external power source!

If however you are plugging in two and each one requires more than 500MA they will need an external power source!

If this is not the case and each device is 500Ma or less you have youre proof!

I think static on the case alone should warrant Apple fixing the device.