There are a number of ways to discuss API popularity. Our metrics are based on developer engagement. The "track" functionality on ProgrammableWeb lets developers declare an interest in receiving updates on particular APIs. Which APIs and categories are seeing the most activity.
Echo, best known for its online commenting tools, recently launched an ambitious service called StreamServer to aid brands in creating their own "white label" social media sites. Media brands like ESPN and Newsweek want to capitalize on the investment in their content. The problem is that the attention of consumers and lucrative revenue streams are focused on on social sites like Twitter and Facebook. Echo StreamServer API aims to tip the balance in favor of brands by offering the tools to forge scalable near real-time social sites of their own.