Back in the day, just being active was all it took to build a decent social media community. The competition was weak and early adopters definitely we rewarded for their presence.
Now, everyone has made it to the dance and are spending a boatload of money on it. In order to build a large and engaged social community you need to embrace the basics of both marketing and psychology and mix in a whole lot of creativity.
Here is a nice little infographic from CMS Wire that lays out 6 key elements that marketers need to focus on when building, and then engaging with, a robust social media community.