Default digital/analog pin state - input or output? (do unused pins need to be grounded to prevent floating inputs)

Projects Programming
5

Ok, but do I NEED to? For example, the "Blink" tutorial built into the Arduino IDE doesn't touch any of the unused pins:

void setup() {
  // initialize digital pin LED_BUILTIN as an output.
  pinMode(LED_BUILTIN, OUTPUT);
}

// the loop function runs over and over again forever
void loop() {
  digitalWrite(LED_BUILTIN, HIGH);   // turn the LED on (HIGH is the voltage level)
  delay(1000);                       // wait for a second
  digitalWrite(LED_BUILTIN, LOW);    // turn the LED off by making the voltage LOW
  delay(1000);                       // wait for a second
}

So for an unused pin, if they're set to 'input' by default and I don't change them to output mode, is there a danger to the board to leave them as floating inputs not pulled high or low via connection to 5v/ground?