pg blogs? Or are you thinking of his essays?
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.