This morning I woke up to find Ev's avatar in my personal tweet stream.
I was a bit taken aback. I don't follow @ev. Did not understand why he showed up. So I followed the link and sure enough he does a fine job explaining this.
Seems like Twitter has a bit of an retweet attribution problem. Here is how they decided to solve it.
"In order to get rid of the attribution
confusion, in your timeline we show the avatar and username of the
original author of the tweet—with the person who retweeted it (whom you
actually follow) in the metadata underneath."
So Fred Wilson, whom I follow, is merely mentioned in small text at the base of the retweet. Ev, who I do not follow, is noted prominently with his avatar and user name.
End result is increased exposure, reach, and influence for users that get retweeted. It will be interesting to see how this effects user behavior.