On cloud services, storing all your files as "objects" is much cheaper than renting a filesystem to store them on. The gist of this article is, "if S3 allowed block-level access, it would be as cheap as S3 and as flexible as a filesystem."
The most powerful sentence in the article is "I can't work out the details." I can't imagine any cloud-services engineer reading this article and thinking, "ooh, I'd never thought of adding block-level access!" I think block-level access is the most-requested feature since S3 was born. The author hasn't described how this will work -- or how S3 works, even.