A few of our clients have shared with us their mobile traffic and forecasts. Quite a few – especially retailers – expect mobile (in this case phones and tablets) to surpass non-mobile traffic by Black Friday if it hasn't happened already. This tipping point will be the catalyst for many discussions:

– What web site is my primary web site? Or is there such a thing if I use responsive design tactics?

– How should I be dividing my resources among screens? The backend infrastructure is shared, but PC front end work still takes the lion's share of resources. 

– Is consumer use of the web changing? 

– Is overall usage climbing with mobile? or is mobile or tablets cannibalizing PC traffic? 

Take a look at Branding Brand's report for more stats and information. It's loaded with good stuff.