In the blink of an eye
That's how long it took, on the glacial scale of media change, for bloggers to completely change the media equation.
Check out this chart of the traffic to Gawker's various blogs: nickdenton: gawker traffic.
In a good day, almost a million people read one of Nick's blogs. In a month, more people read one of his focused blogs than read Car & Driver or the New Republic or probably New York magazine (if we count readers, not subscribers).
How long did this take? A year? Three?
Are you writing ads to run on blogs yet?