Worldwide mobile transactions grew to $106bn in 2011

"Worldwide mobile payment transaction values will surpass $171.5 billion in 2012, a 61.9 percent increase from 2011 values of $105.9 billion, according to Gartner, Inc. The number of mobile payment users will reach 212.2 million in 2012, up from 160.5 million in 2011.
"We expect global mobile transaction volume and value to average 42 percent annual growth between 2011 and 2016, and we are forecasting a market worth $617 billion with 448 million users by 2016," said Sandy Shen, research director at Gartner. "This will bring opportunities for service and solution providers who will need to cater to the local demand patterns to customize their offerings.""

Source:  Press release from Gartner, 29th May 2012

Note - I deliberately don't put prediction onto this site, but I'm including this for the 2011 figures.