Evan Williams explains it with clarity. You may agree or you may not. I'm not sure I do - it seems to structure too aggressively what you can and can't do. Manual retweeting may remain as a least worst option. Or, alternatively, we'll carry on using our Twitter clients - just as we have been doing so up to now.
It's a classic example of eco-system and third party support, though - the give-and-take between originator and business opportunists. A leaf out of Microsoft's book, if there ever was one. So how do these Twitter client developers hope - long-term - to make any money? A sheer and utter mystery to me.