Email has been one of the last holdouts of "services that purely distribute", in an era where Facebook, Twitter, search results, job postings are all tailored/processed by an algorithm before reaching the end user.

In addition, of the things that dominate the finite amount of our "attention" (FB/IG/Google), only email hasn't been fully monetized.

When Inbox first launched, there was a lot of discussion on the end of email as a commodity. However, email's customer today is no longer the user (you and I) but the advertisers' (e.g. context-driven ads in Gmail).

With Inbox, instead of passively showing context-driven ads, Google can take it to the next level similar to what Facebook has done with its newsfeed. From inserting ads/call to actions within the Inbox 'timeline', to forcing advertisers/publishers behavior when it comes to how Inbox interprets/filters/classifies an email (remember the addition of the "Promotions" tab?).

I'd also like to recommend a recent article which talks about how Inbox is the trojan horse for your personal AI which goes into some other points: http://solveforinteresting.com/inbox-is-the-trojan-horse-for...