CrossRoads: I assume you are getting the 800ma number from 4 VCC pins * 200mA/pin?
However, on the Arduino Mega 2560, everything is powered by the single VCC supply pin on the Atmega16U2 (when powered via USB), this pin also has the maximum rating of 200mA, but there is only one of them. This leads me to conclude that the maximum current draw for the Arduino must only be 200 mA. Or am I doing something wrong here?
Grumpy_Mike: I am mostly referring to the 5v line, I'm not drawing much from the I/O pins. If the 5V came directly from the supply, I'd agree, but it doesn't for the USB case... It comes out the 200mA limited pin on the 16U2.