The median political blog reader is a 43 year old man with an annual family income of $80,000. He reads 6 blogs a day for 10 hours a week. 39% have post-graduate degrees. 70% have contributed to a campaign. 69% have bought music, 87% have bought books. 58% say blogs are "extremely useful" sources of information. 52% leave comments on other people's blogs. Just 18% of political blog readers have their own blogs.More detail here. And a story in today's Washington Post on the subject here.