My initial thought is that it could be interesting, but then, after looking at the Russell Davies post, two things occurred to me:
1) Only about 5 people usually tweet at an event which means that seeing the same 5 people's comment come up all the time would feel more like having 5 hecklers than contemporaneous chat.
2) My gut feeling is that it has the potential to pander to an attention deficient population that cannot keep focus on a speaker who has put time and effort into engaging people. The idea of having a twitter feed alongside watching a film in Russell Davies' example appalls me.
Let's not forget what event twittering does best:
Allows simultaneous comment and discussion during natural breaks and then a continuation of that discussion.