See this BBC article about the recent Google report on smartphones / internet access and commerce.
I looked at my stats yeterday and 32% of my visitors come from mobile devices, a huge increase. Six months ago it was a case of updating the sites layouts to make them mobile friendly. If the trend in mobiles continues then by the end of this year mobile access will be more than 50%.
And it's not just global use which is up because of the likes of China and Russia. The same is true for the US and Europe.