According to Chitika, which has been tracking iPad adoption rates on its ad network (three billion ads served monthly across more than 100,000 sites) for some time now. By the end of 2011, the iPad will generate more than two percent of all North American Web traffic.
As of this month, the iPad accounts for 0.83 percent of all traffic on Chitika’s network, research director Daniel Ruby tells me. And at current growth rates, which have been steady since the device’s launch, it should hit 2.3 percent by the end of next year.[Source]