Nancy White observes that We learn (when we listen) when we talk. I suspect we all know this is true but we ignore it in a lot of our processes. It's why there are limits to the value of online discussions. Although Nancy doesn't say it explicitly, I think the thinking-by-talking applies most to spontaneous conversation, not to the recitation of prepared remarks.
It also reinforces my view that when we go to trouble of meeting face-to-face we should focus on conversation and avoid formal presentation. The transfer of data can be done offline and people can absorb it (or ignore it) at their own pace.
Chris Rodgers makes some excellent related points. He suggests that you can't really call what happens online a "conversation", although it has its own value.
Hat tip: David Gurteen's tweet