As the company grows bigger, I suppose it's going to be harder and harder for the CEO to code, given the lack of time.
I think if you're running a tech start-up, it's always nice when the CEO codes from what I've seen, since they understand engineering issues and are usually on the same page with you. I've worked with non technical managers in the past and one of them wanted me to build our application's search in just 2 days.
That being said, trivial coding tasks should be given to engineers and the CEO could just take part in high level design/architecture discussions.