I'm not sure what's the point of this statement. Few successful CEO's blog. Few politicians blog. Few celebrities blog. Few people blog. So what?
PG's essays are THE essays to read if you are an excellent entrepreneur - and if you are - and you make the decision to go to an accelerator - which one do you think you want to go to?
There's a hint of at least two tenuous causative implications there: if you're successful, you ought to think twice before wasting time blogging (ie. blogging by the CEO adds no value to the business). Or the corollary: if you're blogging, chances are you're not yet successful (it's a marker for lack of success). Both are reaching.
Blogging by the CEO (founder) simply means that marketing is (also) done by the CEO. The founders and CEOs who don't blog probably delegate marketing activities to specialists (nothing wrong with that). You delegate when you don't possess the skills to execute. This will probably happen when the founders or CEOs don't possess the technical knowledge or expertise about their own fields.
Edit: but maybe, if one in hundreds will think twice before writing again something like "If you are like me" in their post...
If using that word to describe examples that came before the word was coined is anachronistic, then surely so must be using modern English to discuss, say, the Roman Empire?
To me, the defining characteristics of the blog are as follows :
A collection of texts which are :
1 - Published incrementally as they are written, and chronologically organized.
2 - Meant to be read by a wide audience
3 - Usually not ran past an editor.
4 - Not necessarily sharing any common theme
5 - Usually all have the same author.
I cooked up this definition after noticing that the EWDs had been more or less Dijkstra's blog, long before the Web.
PG's essays obviously fall under this definition as well.
I think the defining feature of a blog that's absent from Graham's essays is that blog posts can be intentionally insubstantial, sometimes containing nothing more than a link, possibly with comments. The least substantial essay Paul Graham has written is probably the one where he clarifies that he's not a racist just because he thinks having a thick accent makes it hard to be a CEO. I don't think he would consider posting intentionally insubstantial content to his list of essays.