Recently Track Social put out a report listing Instagram, MyYearbook, del.icio.us, and Pinterest as the fastest growing social networks in terms of audience size. This may be able to predict the "next big thing" in terms of social online interactions and communities.
"Social growth measures how many new connections a brand is making across the already well-established social media platforms."
The key behind a lot of these up-and-coming social networks is that they are leveraging their brand names and services through huge social networks like Facebook and Twitter. Smaller platforms like Instagram (potentially the best platform for sharing photos) and Pinterest make it incredibly easy to share through these larger social networks, which attract non members to sign up for their services.
These social networks can predict future trends for online activity.
Most of these top growing social networks have similar characteristics: (1) photo-sharing, (2) broadcasting through large social networks (Facebook and Twitter), and (3) there is something uniquely perfect about each of these networks.
MyYearbook is so unique because it is a dating site that stands behind the saying "friends first." Instagram has perfected the art of the photo filter that other "hipster" apps have yet to perfect (however, there are still top Instagram alternatives). Pinterest is unique because it allows you to "pin" photos that also create links and branding opportunities (plus it's incredibly fun - learn how to get started on Pinterest).
But who knows - what's popular today may be gone tomorrow.