So.cl launched in 2011, the same year that Google+ came along, during a time when it probably didn't seem insane to launch a Facebook competitor. Coming from Microsoft Research, the site was first aimed at University students before it opened its doors to the wider public. It carried a tiled look to match the "Metro" design used for Windows 8 on mobile and desktop.
Much like Metro, however, nobody really used it, perhaps because it was never really clear what it was for. It ended up mostly being a site to share and discuss random stuff you found on the internet, something you can already do on Facebook. Unlike Facebook, though, it lacked basic features including the ability to just upload a photo.
In the end, it was a good real-life research experiment for Microsoft Research's Fuse Labs, if nothing else. "In supporting you, So.cl's unique community of creators, we have learned invaluable lessons in what it takes to establish and maintain community as well as novel new ways to make share, and collect digital stuff we love," the team wrote. Now that Microsoft has a real social network with LinkedIn, maybe some of So.cl's features will end up there.