Really? I wasn't quite sure what they meant by injecting ads into the timeline. I thought it meant what the free version of Echofon does, IIRC, which is take a friends_timeline and display it with ads in between, rather than something that add advertisements to a user's statuses.
I think they meant the twitter timeline and not the timeline in a user interface. This article pretty much just says what the twitter blog post says, but after reading it several times it sounds clear to me what they meant.
