This is a nice article, but I disagree with the statement that "most of the time", users are accessing the mobile web via cellular (not WiFi) networks. The data that I have seen on this is that the vast majority of mobile web usage is via WiFi - more than 70-80% of mobile pageloads occur on WiFi networks. (Context: I run the mobile web performance team at Google, part of Chrome.) This is in part because web usage is higher on tablets than on phones, but even on phones we see WiFi being the most commonly used network by far. This is not to say that cellular performance isn't important, but this skew might be somewhat surprising to people working in this area.