Adults are not hanging out on Facebook. They are more likely to respond to status messages than start a conversation on someone's wall (unless it's their birthday of course). Adults aren't really decorating their profiles or making sure that their About Me's are up-to-date. Adults, far more than teens, are using Facebook for its intended purpose as a social utility.
Social media continues to be age-graded. Right now, Twitter is all the rage, but are kids using it? For the most part, no. It's not the act of creating and sharing social nuggets that's the issue. Teens are actively using Facebook status update, MySpace bulletins, and IM away messages to share their views on the day and their mood of the moment.
This last point is especially interesting. Kids are not using Twitter. Kids have a different sense and sensibility on what should be "public". The whole "we live in public in the new times" meme is more a creation of adults than what the Facebook generation experiences.
The NYT Magazine also had an article on the topic. It's a typical example of how many adults confuse the utility of Facebook with that of Classmates.com. The author ends her article with the comment:
In my opinion, this is simply misjudged. Facebook could not be more different than Friendster. The investment in the creation of the social graph on FB by every member is enormous.
Going back to the point on privacy and how Twitter and Facebook, my current thinking is that Twitter is really a feature that makes use of the social graph. It allowed a lower transaction-cost version of thet FB status update, before FB got to it. (Thanks, Ali for triggering the thought on this.) There's a lot more intelligence on Facebook and from a social graph perspective, it will continue to lead. And the social graph is where it will finally convert its attention to value: as the identity layer of the internet.
All of this reminds me of the early process we went through in designing Mondus. It is a privacy-first environment that allowed for extensive control. My friend Batuhan Okur recently commented on this in a private conversation. The problem we faced at Mondus was that it emphasized privacy before it had liquidity. When Facebook was first growing, it did not have the same problem, since it was hatched in semi-private universes: the Universities.
I predict we'll be seeing more utilities for privacy control in Twitter. I wonder if FB status and Twitter will converge or not.