If social media makes your head hurt, here's an interesting way to conceptualise/categorise the whole field. Brian Solis has been renewing this impressive diagram each year since 2008. His diagram ranges far beyond Facebook and Twitter, encompassing photo sharing, crowdsourcing, business networking, location based services, social curation, service networks, social fitness and much more. Not only does it show a vast and increasingly influential array of services, it might help developers intent on trailblazing new subdomains within the social sphere.