Craig Lee wrote:
>
> So the failure mode would most probably be a condition where
> the oscillator won't start? ie. Straight DC on the XTAL lines?
>
> Is the only advantage to using a crystal, the better accuracy?
>

Probably so. It might light off on the third harmonic without the caps,
but I doubt that the uP's osc circuitry could support third overtone
operation. Point being, when you deliberately break the circuit, it's
kind of silly to look for useful, predictable behaviour out of it.

I'm not sure it's even an "advantage" question. From what I've seen, few
people are even taking the care to make sure they get the right type of
crystal, and to load it properly. They get poor stability, off frequency
operation, and don't seem aware that they are using champaign to wash
their windshield.

Many many many applications can use resonators, all you need is a
moderate tolerance for error. Even serial Uarts aren't horribly
demanding.  OTOH, resonators are only now becoming widely available in
surplus for cheap.. Use what you've got, but use it right.