There might not be a strong overlap between LinkedIn users and people in politics or media, but the site has 115 million users in the United States, according to the company, and 28 percent of all Internet users are on it, compared with 23 percent on Twitter, per Pew, so yes, it's still a thing. It's just not a thing for getting news.
Only 3 percent of liberals and 4 percent of conservatives say they've gotten political news on the site in the past week, a Pew study found. Compare that with more than 40 percent for Facebook (which is why Clinton also posted a link to her LinkedIn profile on Facebook). LinkedIn is a site for job hunting and making connections; not for keeping up with election news.
But there's a big incentive for Clinton and other politicians to reach the LinkedIn audience: Its users are older, and thus, more likely to turn up and vote. According to Pew, LinkedIn is the only social network that people ages 30-64 are more likely to be on than people ages 18-29. Fast Company called the site "an untapped treasure trove for political campaigns" in 2011, pointing to Pew data that showed nearly 80 percent of LinkedIn users vote or intend to vote, compared with 62 percent of Twitter users.
But above all, joining LinkedIn was a symbolic move by Clinton to highlight her bona fides as a small business candidate. Clinton published an article on LinkedIn detailing four ways to "jump-start small business" that you wouldn't be blamed for thinking was written by a Republican if you didn't see the byline (she mentions cutting red tape and simplifying taxes for business owners).
Small business owners are tend to lean Republican, so any method to reach them on their turf isn't a bad idea. According to the Small Business Administration, they're older (50 percent are between 50 and 88 years old), male (64 percent), and white (85 percent). And in 2012, Gallup found 57 percent of "business owners" (it didn't specify small versus others) voted for Romney while 37 percent voted for Obama.
LinkedIn might not have the news audience of Twitter or Facebook, but it's a wide open social network for politics, and it reaches a different audience than Clinton's other digital ventures do. Not a bad place to tout your small business platform.