I just had a look at the pins used by the Ethernet SD shield (the currently latest version) and found this documentation
http://www.arduino.cc/playground/Main/ShieldPinUsage
where it says that the shield uses pins 10, 11, 12, 13.
However, in the introduction of the shield
it says:
"Arduino communicates with both the W5100 and SD card using the SPI bus (through the ICSP header). This is on digital pins 11, 12, and 13 on the Duemilanove..."
[...]
"If you're not using one of the peripherals in your program, however, you'll need to explicitly deselect it. To do this with the SD card, set pin 4 as an output and write a high to it. For the W5100, set digital pin 10 as a high output."
So if I understand this correctly, pins 4 and 10 are used to turn either the SD part or the ethernet part on or off.
So if pin 10 per definition is a used one, shouldn't be pin 4 declared as used too?
The question came up because I'm running out of pins soon and have to start bean counting.