UPDATED: Facebook adoption and use by teens is flattening off, according to a new Pew Research study. But Twitter uses is slowly but steadily growing. Eight in ten online teens use some kind of social media, says Pew. Twitter is still not in the same league as Facebook, which attracts 77% of online teens. Still, 24% of online teens now use Twitter, a figure that is up from 16% in 2011. 16% of online adults are Twitter users.