With the proliferation of more and more niche social networks, you have to focus your energies like a laser. If you only have a few hours each week to commit to social media, you need to pinpoint exactly where your customers are. For example, Pinterest is a photo-sharing-pinboard phenomenon that's been heating up in the past 3 months. 80% of users are women and of those women, the majority are in the 25-34 age range. So if your business caters to this demographic, you should consider a presence on Pinterest. But whenever you're thinking of setting up shop on a new network, research what your customers are using and where they are hanging out. Focus your efforts in those places instead of simply "throwing up a profile" on every network you encounter.