"According to the latest research from our Wireless Smartphone Strategies (WSS) service, the number of smartphones in use worldwide surpassed the 1 billion-unit mark for the first time ever in the third quarter of 2012. The first billion smartphones in use worldwide took 16 years to reach, but we forecast the next billion to be achieved in less than three years, by 2015."
-From Strategy Analytics, http://bit.ly/RG6CAL