Facebook added hashtags. Vine added retwee...er, revines, and now Google+ is adding likes--what they call +1s--to your stream. In a few years, each social network will have added so many of the others' features that they'll merge into Tweetbook+, the only site you'll ever need.

Before that dystopian vision comes to life, let's rewind. Google+ on Tuesday quietly rolled out an update that surfaces the content your friends have +1'd and puts it in your stream, similar to what Facebook does with status updates and pages you like.

Your +1s will also show up in your circles' streams, but you can control who can see what you like. If you don't want anyone to see your +1s, you can change your visibility settings following this step-by-step guide.

If friends in your circles are annoying you by +1-ing all over the place, you can turn down the volume on a specific circle (or all the circles). Sadly, you can't turn down the volume of a specific user, but you can put that user in a lone circle and mute their activity.

You can also easily change settings and circles on iOS and Android.

The update is slowly rolling out to all Google+ users, so you might not see it just yet. The feature will show up as a header on an activity card--you might see an update from someone you don't follow, and the header will show you who +1'd that post.

Google+ product manager Shimrit Ben-Yair said in a Tuesday Google+ post that the update is designed to help users find content their friends recommend. The network already shows you popular posts--denoted by a flame to indicate their hotness--and in May added hashtags to help you flip through other, similar posts on the same card. Content discovery is clearly the Google+ M.O. going forward.

And if you want to see the content you've +1'd over the years, you can do that, too.