Alibaba, the e-commerce giant of China, is paying more than $500 million to buy a piece of the Chinese social network Weibo. The site, which already has 46 million users, is expected to grow as China’s middle class expands and connects to the web.

But does social media still have room to grow in countries where it’s been around for a while? Britain’s Guardian newspaper is reporting Facebook received 4 percent fewer visits last month in the U.S. The slowdown could be temporary and is not in and of itself a castatrophe for the company, but that trend extends beyond the U.S. to Canada, Japan and Germany. So, has saturation finally set in?

Lindsey Turrentine, editor in chief of CNET Reviews, says Facebook users may be getting tired communicating with lots and lots of friends.

“There’s a fatigue that goes along with constantly curating your image,” Turrentine says. “Even for younger people, there is something exciting about idea that you could create a small community, that you really only share your thoughts and your feelings with people that you really trust.”

Facebook has competition coming at it from diverse angles. Turrentine says innovation is taking off in the social networking world.

“There’s Instagram — which Facebook purchased partially for its young users. And then there’s a network like Path, which keeps your friend count limited,” Turrentine says. “There’s different examples of different types of social networks that are interesting for different reasons, and users are playing with all of them.”

And while we’re talking about Facebook, there’s new research noting a loose link between social media “likes” and obesity. The open source, peer reviewed journal PLOS One published a study suggesting that people who assign social media “likes” to pursuits involving physical activity — say hiking — might be thinner than people who assign a lot of “likes” to sedentary activities such as watching TV shows.