Facebook, Twitter, Instagram, LinkedIn. These social networks seem so obvious, so simple, so inevitable.

But there were a lot of other social platforms out there, before and after the big Facebook/Twitter explosion of 2008, and their founders, employees, and investors had every reason to believe their creations were going to be the next big thing. We all know the story of MySpace and make jokes about Friendster. But what about other sites that came this close to making it? The stories are interesting, a little sad -- and show us an alternative universe where Mark Zuckerberg just quietly graduated from Harvard.

SixDegrees, 1997-2001

What it was: SixDegrees was Facebook before Facebook. It was based on the idea of meeting friends, romantic partners, and business contacts through the friends of your friends. Users had personal profiles. They could join groups and send messages with each other. It was a multi-purpose site for just hanging out, a step up from chat rooms and bulletin boards. This was in 1997, when most people were using dial-up modems to access AOL.

Why it failed: At its peak, the site had 3.5 million members. But it had trouble turning those users into money via ads, which were primitive at that point, and for which SixDegrees offered no targeting. Users weren't on the site nearly as much as they're on Facebook these days, so its engagement rate was low. There was no photo sharing, which has become a huge part of social media. Eventually, the company simply ran out of money. It was sold to Youthstream Media in 1999 for $125 million -- not bad -- but the new owner shut it down after the dot-com bubble burst. SixDegrees was just ahead of its time.

Pownce, 2007-2008

What it was: Co-founded by Kevin Rose, who co-founded Digg, Pownce was a competitor to Twitter. Pownce also offered document-sharing and threaded message chains to make them easier to follow (a problem I constantly encounter when reading someone's Twitter page). In those ways, Pownce was more like Slack or Yammer, business alternatives to email with elements of live chat. As those apps show, people want those features.

Why it failed: Still, Twitter was first. Every news outlet covering its launch noted this. So Pownce only had so much time and money to grow its user base and find a way to generate revenue. It ran out of time. The company was acquired by SixApart (the creators of Movable Type and TypePad), but even that company saw Pownce's bleak future and immediately shut it down. Also, for some reason, Pownce's tagline was "Send stuff to your friends," but isn't that what people use email for?

Capazoo, 2006-2008

What it was: Friend lists, photos, blogging, video, music...Capazoo really could have been Facebook. Founded by two Canadian brothers, the site launched at almost the exact same time and wasn't limited to colleges like Zuckerberg's creation. Capazoo's users had to pay for access, but also got paid for spending time on the site and undertaking certain activities -- and for bringing in new members. The site had $25 million in the bank and an exclusive content deal with National Lampoon.

Why it failed: Paying users to recruit more paid users struck some, like TechCrunch, as a pyramid scheme. The entry fee of $25 was also off-putting, even in 2007, to people used to engaging in online activities for free. But the site failed because the brothers were embezzling, taking a "commission" from investors on top of their salary. They misspent the rest of the money, increasing the staff to over 100 people, even though they had only tens of thousands of users, nowhere near a sustainable amount. They then sued each other for corruption. Everyone got laid off, the company went bankrupt, and the site was shut down. I'm not sure if the brothers are still speaking to each other.

Yahoo! 360°, 2005-2009

What it was: Yahoo's attempt at a social network. And not their only one; the company beta-launched Mash and Kickstart, which also failed. 360 was a community around blogs, which Tumblr did much better just a few years later.

Why it failed: The New York Times, in a long piece about Yahoo's missteps, dismisses the social network with one sentence, simply saying "it never got caught on." Yahoo has botched a number of can't-miss, foolproof projects and acquisitions, like Flickr and Delicious, so it's no surprise that this social didn't take off, even before Facebook dominated the space. Yahoo claimed that 360 was in beta during its entire four years, so how could it fail if Yahoo wasn't really trying, you know? As Alphabet found with Google Plus, Yahoo users didn't feel the need to create a profile to use all the site's services, from news to search to Yahoo Screen (ugh, another disappointment). But Yahoo had the last laugh: It bought Tumblr in 2013.

Jason Ginsburg was social media editor at Flavorwire and social media producer at Science Channel.

Jason Ginsburg

Weird Social Networks and Why They Failed