The smart phone audience is creeping closer to PC audience levels. By the end of 2012, if smart phone penetration reaches 60%, there will be nearly 150 million users in the US. Nielsen says that mobile audience is 237 million subscribers, while comScore puts it at 234 million. These figures are probably slightly low. A better “base” is closer to 250 million, although CTIA says there are more than 300 million wireless subscriptions in the US (indicating some level of duplication). Read the rest at i2G.