That only works when your content fits on a screen because it messes with the scrolling-based nature of the web (or screen content in general – just picture how awkward it is to read an A4-portrait multi-column PDF with fit-to-width on screen).
Personally, I like well-columned stuff switching to scroll horizontally.
(It's one of the things I loved about the design style of Windows 8 apps that has been lost in the Windows 8 hate, and admittedly was a part of the Windows 8 hate, because people don't respect a good horizontal scroll of columnar reading material, sigh.)
