Today in Social

Earlier this week, Twitter turned five and today professional social network LinkedIn said it reached 100 million members. Those are two “niche” social networks – niche in that they’re organized around specific functions or contexts – that have grown up. I’m a believer in focused social networks; I don’t think Facebook always delivers context, and there are ways to use it and other marketing techniques to build audiences relatively inexpensively. MSNBC.com is relaunching hyperlocal content aggregator EveryBlock as something like a neighborhood social network. Other than enabling Facebook or Twitter log-ins, it doesn’t seem to be leveraging other social networks much. Of course, using open APIs without a negotiated agreement in place carries its own set of risks.