Verizon is up to more than 12% of all iPhone web usage, based on data from the Chitika ad network (http://www.chitika.com).

“The data is based on a 24-hour rolling period, so it’s a good snapshot of what iPhones are in use right now,” says Chitika. “For Verizon to pick up that big of a share of iPhone users in about a month is impressive, and doesn’t bode particularly well for AT&T.”

One day after the Verizon iPhone launched to the general public, it accounted for 3% of the U.S. iPhone base. Data is based on iPhones across the Chitika advertising network. Only traffic on cellular connections is recorded. Percentages are a 24-hour rolling average, updated hourly.