I got the impression from the blog post that the President's team disabled that feature for fairly obvious reasons (i.e. can't really let 10K+ people chime in).

I got the impression from the blog post that the President's team disabled that feature for fairly obvious reasons (i.e. can't really let 10K+ people chime in). Here: "Unfortunately the call was marketed and promoted as a “conference call” and questions were invited in advance [...] which does happen to be what Mixlr is intended for [...] However, in the end they didn’t really use it that way nor to the extent of what Mixlr allows and it was just a one-way broadcast." (from the eighth paragraph in)