How would it damage the pin? An input pin is high impedance.
doh! so the pull-up is just for avoiding floating values.
pinMode(pin, INPUT_PULLUP); works on IDE v1.0 and up
One line of code less. Nice.
BTW, even if the pins default to INPUT, IMHO it is a good practice to explicitly set the mode. Sort of self-documenting software.
My circuit has some normally-open buttons. I was concerned about the possibility of having them pressed before the pin was configured. I see that there is no reason for worrying.