I figured out exactly what bugs me about Twitter and Facebook showing your friends’ “likes” in the timeline. It’s not just that they’re public — that’s true on Tumblr or Flickr or Instagram too, but you only see them when you choose to look for them.

It’s that broadcasting likes in the newsfeed blurs your intent.

• A “like” is a message to the original post’s author (and a bookmark for yourself).
• A retweet or share is a message to your friends or followers.

Putting them in your followers’ feeds turns a “like” into a message to them as well, even though it’s not what you intended. (If you wanted to share it, you would have shared it, right?) It’s a step above completely frictionless sharing, but it still messes with the signal/noise ratio of the timeline.