Pinterest gets an F. By default, Pinterest presents the users with a minimum of four columns of undifferentiated emphasis. As you expand your browser or shrink the size of text on the screen, Pinterest scales up the number of columns to a huge number. Pinterest has been successful among early users. But as their user-base grows, they'll need to fix their interface to embrace linearity, or they'll wither.
Instapaper gets an A on their browser and phone apps, which are perfectly linear in reverse-chronological order. But their tablet app presents users with two equal columns of content. I give their tablet app a D. Why they chose to go two columns on the tablet is a mystery.
You'll note that these examples of bad, multi-stream design are all sites or apps that you could argue are very successful, thus invalidating my premise. But the same could be said for Facebook, and that company is apparently fixing its multi-stream problem in order to keep expanding into the larger mainstream user base.
Multi-stream social content feeds tend to be appealing to technical people, early adopters and tech pundits, who drive the early success of some of these apps and create a false sense of confidence for the companies who make them.
But the larger market -- stressed out, type-A personality "skimming" executives, older people less comfortable with screen clutter, non-technical users, teenagers, people reading content in a second language -- who collectively make up the "mainstream" user base will choose a linear interface over a non-linear one.
When the dust settles on the ongoing war over eyeballs in the social content space, the winners will all have linear, single-stream content interfaces.
Who's doing it right
Google+ in a browser also gets an A. The company offers a Twitter-like stream of perfect linearity. In fact, they even got a lot of flak from the nerdy techie segment of their audience for not filling up all the white space on the interface. It's interesting to note that a failed precursor to Google+, called Google Wave, suffered from a two-stream layout, which was awful and contributed to its failure. The phone app for Google+ is also very linear. (The tablet app, not so much.)
The Fancy gets a B+. They have a single, linear stream, for the most part, but every few items they'll slot two items in side-by-side. It's not a visual disaster, but it does represent the primacy of being "different" over user appeal.
One stream to rule them all
We live in the age of the social content stream. Users are gravitating to social content streams because they bring order to chaos, and give people a sense of context -- usually time context.
The thing is, an interface with more than one visually equal stream of content isn't a stream at all. It's just more visual chaos.
Users will ultimately gravitate to the sites, services and apps that can give them a single stream that presents social content in a single, orderly stream of updates. Twitter is already there. Google+ is there. And Facebook is getting there.
All those other sites will either figure out that linear rules, or they'll fade away into oblivion.
Read more about social media in Computerworld's Social Media Topic Center.