Google's got clout with savvy youth
The marketshare of US visits to Google's Gmail increased 17 percent from February 2007 to April 2007 and was up 30 percent from April 2006 to April 2007, writes MarketingCharts (via Hitwise). Google's Gmail opened up access to all on February 14, 2007.
Yahoo Mail and Hotmail, however, remain the dominant Web-based email services: Yahoo's April 2007 share of visits was 13 times greater than Gmail's; Hotmail's was 6 times greater.

Gmail users, though, are in some ways a more attractive demographic than those of Yahoo Mail and Hotmail, which more closely resemble the general online population in age and socioeconomic status. Gmail users tend to be younger, with higher incomes, and are generally early adopters.
For the four weeks ending April 28, 2007, 54 percent of Gmail visits were from users age 18-34, compared with 42 percent for Yahoo Mail and 44 percent for Hotmail, according to Claritas PRIZM NE social group data (via Hitwise).

Some 18 percent of Gmail's visits were from those with average annual household incomes between $100,000 and $149,999, compared with 15 percent visiting Hotmail and 13 percent visiting Yahoo Mail.
Gmail users are also more likely to be Facebook users: 3.7 percent of Gmail's downstream went to Facebook in April 2007, compared with 2.2 percent for Hotmail and 1.2 percent for Yahoo Mail.
Image courtesy of ABC.net.au.