Emil Protalinski has a much more thorough analysis of what is happening, which includes the Pew Research report AP used, as well as a July 2011 Pew report that focused solely on teens and social media use. His conclusion? Teens are definitely using Twitter more, but they are not giving up their Facebook accounts to do so.
The numbers in the July 2011 report "were much more telling: of teenagers who use just one social network, 89 percent are using Facebook," Protalinski wrote. "Less than 1 percent are using just Twitter. Of teenagers who have more than one social network, 99 percent are using Facebook, and 29 percent are using Twitter as well."
The AP report seemed aimed at the myth that younger users found Twitter "uncool" and less protective of their privacy. AP draws some solid conclusions on why teens may be using Twitter more than they once did: unlike Facebook, Twitter allows them to set up multiple accounts and they can do so anonymously. There's also rising evidence that teens like to use Twitter with a smaller, select group of friends while keeping Facebook as a more public profile for a wider group of friends and family members.
But score a big swing-and-a-miss for the assertion that teens are "shifting to Twitter" included in the AP report. Like a lot of us, teens, including at least one of the two teens AP quoted in its story, maintain multiple social media accounts on multiple social media platforms.
Anecdotally, I can't speak for teens, but as a part-time college writing and journalism instructor, I can say Twitter has been the best crossover platform for me when it comes to connecting with students in their late teens and early twenties. There's a growing body of evidence suggesting that social media in the classroom can increase student engagement, so I've been experimenting with different ways to do just that over the course of the past year.
For many students and faculty, there remains a creep factor for friending on Facebook. I also know of a handful of students who have been in abusive relationships and have either been advised to shut down their Facebook accounts or limit the number of friends they have while amping up their privacy settings.
I tried using Google+ in one of my classes last fall but ran into problems when a couple of 17-year-old freshmen couldn't register for the site (Google has since changed the policy and opened Google+ up to teens). Google+ was still relatively new at the time, so there was a lot of class time wasted in getting students up to speed with its many features.
While not all students love using Twitter, it is workable in most situations. Roughly half of my students have Twitter accounts before they enroll in my class, and for those that don't, its a simple enough platform that I don't have to spend loads of time demonstrating the basics in class. Students who are truly worried about their professor creeping on their Twitter feed can easily and quickly set up a new one (which is something I recommend they do).