Great infographic! It goes nicely with one I shared today with social media stats. Joining LinkedIn groups is one of my favorite tips (it's how I discovered this article!), and the infographic I shared says that there are 1.5 million groups to choose from, and that 81% of users are in at least one of the groups: http://www.meltwater.com/social-media-blog/did-you-know-social-media-stats-for-2013/. Those other 19% need to get on it!