Came across this nice sheet at cmo.com that tries to give insights into which social media tools are the best in terms of offering bang for the buck, namely by way of Customer communication, Brand Exposure, getting traffic to your site and of course, SEO.

Of course, this is not a solution in itself, but a good starting point at least. How does your company determine marketing strategy in terms of which social media sites to use?

The Social Media Landscape