And that's where multi-column social content streams come from. They come from a company political culture where engineers do the design, or overrule the designers, especially engineers who believe every bit of empty space should be filled with content, and that using design to emphasize specific visual points of entry and provide hierarchies of content is arbitrary and unnecessary.

Social and content apps and sites live or die by the unmeasurable quality of their user interfaces. Most users are unable to tell you why they like, or don't like, use or don't use a specific user interface. You can ask them, but they can't tell you.

All social applications that have been successful over the long term have presented incoming messages in a linear format, with a single stream ranked by reverse-chronological order or "best" first or some other method: Email, instant messaging, texting, and others always provide perfect linearity. For social content, this is the only system that provides broad-based, international mainstream users with peace of mind and a sense of contextual awareness.

You don't want to fill every square inch of a content interface of any kind with content for the same reason you don't want to fill every square inch of your home with "stuff." The most beautiful and pleasant homes tend to have lots of unused open space.