What's the message displayed by Gmail when there's no message in your inbox? If you answered "No new mail! Want to read updates from your favorite sites? Try Google Reader", you are right. It was Google's subtle way to promote Google Reader.
Before Google Reader was released, Gmail's "inbox zero" message used to be: "No new mail! There's always Google News if you're looking for something to read."
Now that Google focuses on developing Google+, a modern version of Google Reader, Gmail's new message is: "No new mail! See what people are talking about on Google+." The links sends Gmail users to the "what's hot" section of Google+ which "highlights selected content thought to be exemplary, interesting, and appropriate: showing you serendipitous and diverse information".
From Google News to Google Reader and now Google+, Gmail illustrates three different ways to read news. Google News ranks and clusters articles from the web, Google Reader allows you to read news from your favorite sites, while Google+ lets you read the articles shared by the people you follow. From news that are important to everyone to news that are important to the people you trust.