E-commerce has been running at the rate of 15% annual growth for many years, but is just 8% of retail sales. That seems tiny in relation to what we've seen happen to print promotions like catalogs and direct mail, and the rise of zombie or troubled shopping malls. The problem is that big ticket items, like autos, raise the size of retail sales. Those items may be researched online, but their actual purchase is not made until it is transacted at a car dealer. Restaurant purchases are also a distorting issue in the data. 

This chart explains it a little better. E-commerce sales is at the bottom (red line). In the second quarter, it was just short of $100 billion. The blue line is retail sales less vehicles and parts. The green line has food service sales deducted. The black line had e-commerce sales deducted, and shows retail sales through traditional channels. Those sales through older channels are lower than they were at the start of the recession. All of the growth in non-auto and non-restaurant retail for the last decade has occurred in e-commerce channels.