Zuckerberg being a terrible speaker (2010): http://www.youtube.com/watch?v=o3hu3iG8B2g

Zuckerberg being a brilliant speaker (2011): http://www.youtube.com/watch?v=1OQQ4E2k0Mk

Notice how he seems to be more confident and relaxed when he speaks. Unlike in the AllThingsD interview, this time he uses pauses and gestures effectively as well.

Just to be clear, that's not Zuckerberg for the first five minutes in the 2011 video.