So just how big is mobile commerce? In a recent report from Forrester, it is estimated that mobile commerce will top $6 billion by the end of 2011, and grow at an annual rate of 39% through to 2016 to $31 billion. This means that by 2016, mobile commerce will still only account for 7% of overall online sales.

And according to a recent survey by eMarketer, the most popular reason for using a smartphone while shopping is to compare prices of products and services (purchasing ranked as least popular reason).

However, while mobile commerce may be a relatively small percentage of online sales today, the growth of smartphones indicates it cannot be ignored. According to comScore, there are 234 million mobile users in the U.S. and of these 48% (112.3 million) can access the Internet.

The introduction of the tablet will also have implications for mobile shopping. Forrester found that consumers, who have both a smartphone and tablet, prefer to shop on the tablet because it has a larger screen. They report that in 2010, there were 10.3 million tablet users and they project this number will increase to 82.1 million by 2015.

Mobile commerce will grow and continue to evolve. While it may not be quite there yet, increasing adoption of smartphones, introduction of new devices like the iPad, and increasing customer expectations will no doubt see its contribution to online sales increase.