When you review items in the Google Play Store, or engage with the recommendations of others, you're actually using Google+ without visiting the site.
When you comment on a blog that's using Google's own Blogger you're probably using Google+ and interacting with Google+ users without going to Google+. (And the people you interact with don't even know you're not on the Google+ site.)
And to use Google Glass is to constantly use Google+ without going there. Posts, birthdays and other content comes to you. When you choose to "share," from Google Glass, that goes out by default to Google+ as well. And the cloud storage site for pictures, which are automatically backed up, is Google+.
Google's aggressive integration of Google+ social features into so many of its products hasn't felt like the "social layer" Gundotra described. To fans, it has felt like the improvement of Google services with Google+ features and to critics, like the forced usage of Google+.
But the integration of Google+ and Google Display Network advertising really feels like a "social layer," and for two reasons.
First, the end result fully benefits every party involved -- the advertiser, the user and Google -- without compromise.
The +Post ad appears on a site as a 100% display ad, plus social features. And any display ad can be made into a +Post ad by the advertising company simply by posting it as the picture in a Google+ post and then filing into the +Post system.
When you click on any display ad, you expect something to happen that enables you to learn more and possibly interact in some way -- today you expect that a new tab will be opened, a new page loaded and your attention directed to that new page. But with a +Post ad, you stay on the same page with the social post on top. In that sense, the experience of engaging with the ad isn't diminished by social features, but improved. And the resulting post that rises over the page is a familiar social post displaying the comments of other real people and inviting your interaction.
And, of course, it's great for Google because every +Post ad is also an ad for both Google+ and Google Display Network.
That's what a "social layer" should do -- add social value without taking away anything.
And the second reason +Post ads feel like a "social layer" is that instead of social features on Google sites, these are social features on non-Google sites. Once +Post ads are made available to all advertisers, Google+ DNA could appear on 2 million web sites. It's going to feel extremely “social layerish” to find ads on random sites transform into Google+ posts on those sites.
Google's "social layer" has been around for more than two years, but only on fewer than a dozen or so Google sites. Soon, the “layer” will be on 2 million more.
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