Worrying about your parents being on the same social network as yourself ceases to be an issue when you become an adult yourself, and you no longer have to hide the fact that you were out partying when you were supposed to be studying at a friend's house. And as the GP notes, Facebook solves the problem that teens haven't yet had to confront - how do you catch up with your friends when you don't seem them several times a week?
In fact, the thing that has made Facebook such a phenomenon is not that teens found it cool, but rather that the much larger older population found it useful. I would be willing to bet that teens don't even make up 10% of Facebook at this point in time. When adults stop posting and stop receiving notifications on Facebook, then Facebook has something to worry about. Until then, my money would be on teens gravitating back to Facebook as they get older, and being cool becomes less important than knowing that all of your friends are contactable on Facebook.
Remember your Clay Christensen: The late majority follow the early adopters. In this case, this means where the teenagers move to, that is where the parents will eventually go. The writing has been on the wall for this for a few years now -- FB doesn't stand a chance to last out the decade.
Teenagers as a group are not trendsetters for other age groups, for example when did you ever see a Justin Bieber hairdo on anyone over the age of 17?
They are time rich and money poor, a situation that reverses as you get older. They live geographically close to most of their friends. This is mostly not true for adults, who tend to be time poor, wealthier than teenagers, and geographically separated from their friends. Because of this, looking to teenagers to understand what most people want from their social media does not seem like a particularly good idea to me.
"In this case" because remember -- they were the ones that started the migration to FB; in this case, they were exactly "the trendsetters for other age groups" and so if they move, your early adopters are moving and the late majority will follow.
Additionally, non-facebook users will find that when they go to college, they won't know when any of the parties are (and they won't know about any of the study groups). If you're a person that has that typical human need to belong, university almost forces you to log into facebook.
Anecdote: I'm 55 and I do not have a facebook account. I was recently taken severely to task for this grave omission by cousins, one in her late 60s and the other in his early 70s.
That is a big and growing market, as the 'silver surfers' increase their smartphone/tablet skills and find the web applications that enable them to achieve a major goal: contacting far flung family.
I may have to cave in because they want to use FB for organising family meetups (this is an extended mafia with branches on 4 continents by the way).
Facebook solves the problem that teens haven't yet had to confront - how do you catch up with your friends when you don't seem them several times a week?
Twitter. Every teen I know, though admittedly a small sample, says that facebook is for old people and twitter is the way they communicate with each other. Constantly.
Until then, my money would be on teens gravitating back to Facebook as they get older...knowing that all of your friends are contactable on Facebook. No they won't be. The ones in their social circle will be on twitter or something like that that replaces it. Facebook will gray out; even the older people I know that haven't deleted their profile yet are getting tired of it.
In fact, the thing that has made Facebook such a phenomenon is not that teens found it cool, but rather that the much larger older population found it useful. I would be willing to bet that teens don't even make up 10% of Facebook at this point in time. When adults stop posting and stop receiving notifications on Facebook, then Facebook has something to worry about. Until then, my money would be on teens gravitating back to Facebook as they get older, and being cool becomes less important than knowing that all of your friends are contactable on Facebook.