These stats are what Opera sees from users of its Mini browser. Opera Mini runs data through Opera's servers to compress it before sending it to the client, This is necessary for some people with limited data plans or phones with slower processors and small amounts of RAM. It also gives Opera a chance to generate a ton of statistics.
Pages per month has jumped from around two billion at the beginning of 2008 to fifteen billion today. Data has increased from around 25 terabytes to nearly 230 terabytes in the same time frame. Keep in mind that is just for one browser. You can assume that the other browsers on the major smartphone makers have probably seen similar increases
The full report is here. It includes a lot of stats and breaks it down by major market, such as the US, the UK, South Africa and China. The most disturbing statistic is the monthly data cost per country. The US is the highest at $2/MB. That may be skewed due to users buying all-you-can-eat data plans and doing little more than using it for email or occasionally checking stock quotes, the weather or sports scores.