Yep that was my initial reaction to this too, someone will want to listen to it enough to automate the recording of it which could easily be published or used out of context to cause more damage. Audio drivers such as soundflower for OSX coupled with a simple scripts would probably make this possible.
I have to say I just don't get the OP logic for having the live only mumble sessions. Also this seemingly increased need for censorship that floating about everywhere at the moment. Everyone should realise, Chinese included, that parts of the mumble sessions, and other discussions, are off the cuff and brainstorm like in nature. If Dan or anyone else suggests something sub-optimal people should have the sense to realise that it does not mean that it is enshrined future policy. We usually correct course pretty quickly and open and public debate is instrumental in allowing the course-correcting to occur as swiftly as possible.
I do agree that certain things should not be discussed in public if they might be considered very controversial, especially if they are brought forward by prominent members of the team such as Dan. I'm sure that is already the case and that much more radical ideas have been discussed by various teams that only a few have been privvy too.
To combat the controversial issues perhaps there should be a second monthly mumble sessions that only the 100 elected delegates can attend that is not recorded or made public. This could operate on the Chatham House Rule, (i.e. what was discussed can be disclosed publicly, but who said it cannot).
http://en.wikipedia.org/wiki/Chatham_House_RuleSomeone could be responsible for summarising the this private session, fuzzy?, and perhaps it would allow BM to save anything that might be considered a little controversial for these more private sessions instead of the main Mumble sessions.
Just a thought - not sure how practical it would be give the time it might take to summarise what was discussed. Also it relies on every one of the delegates agreeing to keep true to the Chatham House Rule and not disclosing who said what or recording the session.