Here is the output of a conversation I had on G+ few days ago… the quality of the comments was so good, that I thought it make sense to put it here. First source that brought to my attention was from Forrester. It’s a very cool tool to let you see how people in certain ages are interacting with social sites.
The other source, is a presentation that give some insight about the % of people that create content for the world to consume.
Here is a short example. You can see what is the break down for the age group of 35-44/USA/Female (you have 2 guess, on why I’ve choose it).
BTW, there is a good post by Mr. Wilson about this subject and how twitter usage is ‘similar’.