Many people weren’t happy with the sudden appearance of timeline notifications about Twitter accounts their friends followed or the tweets their friends favorited.  There was hope it could be an experiment, as it didn’t seem to show on everyone’s timelines.  But it would appear that it is here to stay as Twitter has confirmed the change in their help pages for “What’s a Twitter timeline?“.

Here was the help document as of two days ago.

And here is the new version of the page, with the new addition.

They have since added:

Additionally, when we identify a Tweet, an account to follow, or other content that’s popular or relevant, we may add it to your timeline. This means you will sometimes see Tweets from accounts you don’t follow. We select each Tweet using a variety of signals, including how popular it is and how people in your network are interacting with it. Our goal is to make your home timeline even more relevant and interesting.

This is interesting because many people were reporting there wasn’t anything obvious about what was showing in their stream – some weren’t popular tweets nor popular accounts.

Bottom line, you better get used to Twitter inserting activity from the people you follow based on what they favorite and follow.