There's a real beauty to Facebook for adults. It allows us to keep track of things that are happening in the lives of those important to us such as friends, coworkers, family, and those who are distant from us. It's for this reason that the hoopla about Facebook losing too many teens is being misunderstood by many, including Facebook itself.
Here's the thing. Facebook isn't cool. It hasn't been cool for a couple of years. It was cool before more adults started getting on it. Now it's a drag, at least from a teen perspective. They see their parents spending as much if not more time on it than they were and they simply don't want to be using the same social network as them. It's pretty natural. Few teens want to be hanging out in the same places that their grandparents hang.
More importantly, they don't have to. The people that they want to interact with are the people that they see for several hours five days per week. For the most part, their world is isolated to their friends from school. Facebook brings no additional value to fulfill their lives the way it does with adults. As some flock to Instagram, Twitter, and other social networks, it's natural to see this sort of exodus.
They'll be back.
When they graduate and they really want to know more about people than what they can see in 140-characters or less or what they can discover from a 15-second video, they'll turn to the same place they abandoned. When their friends go off to different colleges, take on different jobs, and move to different states or countries, they'll want to keep tabs on them in ways that only Facebook can deliver.
This isn't the end of Facebook. Kids might be the driving force that makes networks popular, but Facebook has reach a self-sustainability point. They are flocking away from it now, but they will flock right back to it in the future. They'll have to when they can no longer see their ex-boyfriend and who he's talking to in the lunch line. Businesses must understand this in order to make appropriate decisions about whether or not to invest in Facebook as an advertising venue. As Zach Billings mentioned in a blog post the other day, "If your target audience is an older crowd, then Facebook is still the social network of choice."
If your future target audience is the teens that will some day be adults, then you should still stick with Facebook.