Just as Facebook changed its policy to let minors make public posts, Piper Jaffray published results from its extensive youth survey that indicate Facebook is no longer the most important social network to adolescents. Facebook's popularity among young Americans has been trending downwards for a while now as younger services such as Twitter, Instagram or Tumblr have been gettig more attention. Given the numbers shown in the chart above, Facebook's decision to acquire Instagram appears very smart in retrospect, as the photo sharing platform proves immensely popular with a younger audience.