This is basically a nifty implmentation of the paper I published last year (PDF), except Chinswing has left out a core affordance: easy quoting.  Without quoting, context and quick browsing decrease in quality.  Still, it's neat to see this tech in beta, I think there is potential here.  YouTube's "video reply" service is similar except, again, without quoting.  When we did our user study in the aforementioned paper, we decided to go with a mobile client because that's where such content may make the most sense.