It is based on an online research study conducted in September 2007 and illustrates the way in which use of social media varies within the IT professional community. Please don't take the absolute percentages literally as this was a self-selecting sample which would have been biased towards those with an interests in social media
You should also bear in mind that research over 6 months old (as this is) will not necessarily reflect the position today in such a fast moving area like social media. We'll repeat this study at some point and do some proper trending, but in the meantime, here are the raw charts - deliberately without commentary:
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