With last week’s news of YouTube’s acquisition for $1.65 billion, I thought I’d take an opportunity to post a chart that demonstrates the company’s quick growth from obscurity in October 2005 to market dominance in mid-2006. The chart below depicts the market share of visits to YouTube.com based on all internet visits in the U.S.

One phenonomenon that we’ve found in the adoption of 2.0 sites is that the difference in site demographics from the early days to market dominance demonstrates who the early adopters of 2.0 apps are. YouTube is a perfect example of that. Below are the demographics of visitors to YouTube in January 2006:
YouTube.com Demographics January 2006

When comparing the demographic snapshot above to the one below which captures the four weeks ending October 7, 2006, it highlights the difference between the early YouTube visitor compared to today’s mainstream user is that of age (with 18-24 year olds dominating) and to a lesser degree socioeconomic status (as evidenced by lower household income, likely college students, and higher household income of $150K plus), but independent of sex and geographic region.
YouTube.com Demographics October 2006

For a very interesting discussion of the definition of Web 2.0 see this report issued by Pew Internet. Mary Madden and Susannah Fox (with the help of some Hitwise charts) provide some great examples of 2.0 sites and their growth when compared to 1.0 counterparts.