Resistor on pin 1 needed?

I've just built an arduino clone using a atmega328 chip. It seems to work just fine without a resistor on pin 1.

I was under the impression it would continually reset without it?

or have I just gotten the wrong end of the stick....?

I believe there is a weak internal pull-up on pin 1.

Previous discussions have gone ovef erratic behavior without the external pullup. Atmel Application notes seem to suggest having one, especially with DTR cap, external reset switch connected.

I have personally had zero problems with it while tinkering around, but I have never left it out on something that's going further than a evening on the breadboard, as I have been able to reset the chip by waving my finger over it once before

Yes it will work without it but not reliably. That means under all conditions of noise and temprature.

The internal pull up is very weak. I built an attiny13 project and without and external pullup resistor, it occasionally resets by itself.