The day some investors have been fearing may be here. A survey conducted by Piper Jaffray suggests that Facebook Inc (NASDAQ:FB) is no longer the most popular social network among teenagers. Twitter has become more important, but Instagram is catching up fast.

Facebook and Teens

Facebook in “Taking Stock with Teens”

This is the 26th semi-annual “Taking Stock with Teens” survey conducted by the firm. It focuses on consumer insights and indicates that social networks do play a key role in teens’ decisions. In fact, more than half of teens who took part in the survey indicated that social networks are important when it comes to deciding what to buy. And when it comes to teen decisions, they name Twitter as being the most important social network when it comes to the decisions they make about what they buy.

Facebook Inc (NASDAQ:FB) took second place in that category, while Instagram came in third. According to the survey, 23% of teens say Facebook is the most important social network, compared with 33% six months ago and 42% a year ago.

Instagram gains on Facebook and Twitter

Business Insider’s Jim Edwards broke down the results further, saying Instagram is tied with Facebook as 23% of teens say Instagram is the most important. That’s compared to 12% one year ago. Twitter only edges out the two sites as 26% of teens say it is the most important. If Instagram keeps gaining at the same rate, it will surpass Twitter before too long.

Edwards also points to a recent Pew report which also suggests that Instagram could overtake both Facebook Inc (NASDAQ:FB) and Twitter. If Instagram is the next big wave in social networking, then Facebook’s decision to acquire it was a spectacular move.

Are teens really dumping Facebook?

Facebook Inc (NASDAQ:FB) has been addressing concerns about falling teen engagement for quite some time. Founder and CEO Mark Zuckerberg said their research shows teens actually aren’t abandoning the social network. However, the company hasn’t shared that research publicly. The social network has also been making some changes geared toward teens, like some recent modifications to its privacy settings.

According to Edwards, two sources at Facebook say there’s a difference “between what teens say about Facebook and how they actually use it.” He said Facebook might be “uncool” because teens’ moms are on it, but it is still a ubiquitous tool.” The typical teenager has 300 friends on Facebook but just 79 followers on Twitter, according to Pew.