Not every social media channel is right for your business. It sounds obvious, but not every business heeds it. You are better off concentrating and doing a good job on fewer channels than spreading yourself too thin.
This infographic by Bizcatalyst360 shows some great trends, namely that if you are a B2B you should concentrate on Twitter, Linkedin and Google +.
Customer-driven businesses on the other hand, will find a better fit with Pinterest, YouTube or Facebook, especially if they're visually inclined.