What are some of the best books you've read? I tend to be pretty disappointed with most books.

but the signal to noise ratio of finding good content is much much higher for online (IME)

Yeah, I think there is low-hanging fruit in assembling collections of great blog posts.

I think the real issue here is the return of posting an article vs. reading a book, not of reading an article vs. reading a book.

It's definitely relevant though because internet reading trades off against book reading for the people who will read your post. It's possible that there is some kind of power law distribution of post quality, and a small number of blog posts generate a large fraction of the value for readers. But it may be hard to predict how much value you will generate for your readers in advance--for example, I didn't predict this post would be as well-received as it was.