The big content is for the people who jump into the site and want to read just a few articles. It's the "most important". It gets clicks. The people who sit on the site all day are going to appreciate the left column, but it doesn't have the same prominence, because we already have their attention.

By throwing the big stuff on the right, we're also making people who jump into the site for the big stuff move their eyes across the content, which might prompt a click.

We've thought very hard about who our site is designed for and the path their eyes will take. The column hierarchy is designed for different groups of people looking for different content.