[hombre_fatal]

There are good faith arguments for applying smarter sorting / filtering to the stream.

For example, if someone follows two people and one person simply tweets at 1000x the rate of the other, I would argue that it would be better UX if the rare tweet from the other person gets more weight.

Another thing Twitter does is show you popular things that have been liked by the people you follow. It might be way too much to show you every thing that every person you follow has liked every time. But it can introduce some interesting content to your stream to see such second-tier content.

I don't see how promoted content plays into it since you can interpolate it anywhere.