When Instagram founders Kevin Systrom and Mike Krieger announced plans to leave in September, reports surfaced of disagreements over Facebook’s level of involvement with the company. It’s easy to see why: Instagram has avoided most of the reputation problems Facebook suffered over the past several years and in doing so, Instagram has shown strong user growth.

Last year, Instagram’s worldwide monthly user base increased nearly 20%, to 713.9 million users (note that our estimate factors out duplicate, spam, business and other nonhuman users). And we expect the number of users to continue growing, reaching 989.1 million by 2022.

But Instagram’s future is deeply intertwined with Facebook. Much of its ad business growth—worldwide revenues more than doubled last year to $9 billion, we estimate—has come because extending an ad buy to Instagram is as easy as checking a box in Facebook’s ad manager. And features like Instagram Stories have been highly successful, putting pressure on the app to continue delivering hit marketing concepts.

In our recent report, “US Social Trends for 2019,” we predict that Instagram will experience some growing pains this year. Some of the challenges the social network could face include user dissatisfaction over the growing ad load, an increase in the use of the platform for bullying/trolling and election meddling.

In late 2018, a US Senate Intelligence Committee-commissioned report revealed that the Russian Internet Research Agency relied heavily on Instagram to spread misinformation and stoke discontent during the 2016 election and beyond. The report found that Instagram was more effective at driving engagement with such content than Facebook or Twitter.

While most eyes will be on Facebook—we expect the company will continue to profit, but usage problems will persist—it will be wise to watch for signs of trouble on Instagram as well.

For more predictions for social media in 2019, eMarketer PRO subscribers can read our "US Social Trends for 2019" report now.

Not sure if your company subscribes? Check here.