[charlesarthur]

"The author needs to clarify what portion of total revenue Google derives from ads, and then to break those ads out by service (Youtube, Gmail, Sponsored search), platform (desktop vs. mobile), and geography."

The author (me) would love to, but Google makes very little data available. The only geographic data is total revenues broken down by US/UK/Rest of World. There's also revenue from "Google [search]", "platforms" and "other". Estimates about YouTube etc revenue tend to be calculations based on various private metrics.

"I'd wager… that Google never planned to make much money from mobile search in the first place"

Possible. As the article says, and has been repeated multiple times, Android was a defensive move to stop Microsoft cornering the mobile search field.

"People don't explore on their smartphones: they consume."

I must introduce you to some networks called "Instagram" and "Snapchat" and "Line" and "Weibo" and "WhatsApp".