One of the lessons learned at the MediaWiki Developer Summit is that video recording is indeed useful for some sessions. We need to have a default plan for tech events in general, and start applying it at the #Wikimedia-Hackathon-2015.
The primary goal is to record one-to-many sessions that will still be useful to watch in, say, one year. Sessions where a speaker exposes an idea, and then asks the audience for questions.
Erik and Damon's opening session and the Dev Summit is a good example, because they transmitted a vision for the future with little interruption. Tutorials and training sessions are also good examples.
Recording smaller meetings, brainstorming sessions, etc, is not a goal per se. Video recording can actually hamper the live discussion, and session organizers can always find low-tech solutions like Google Hangout-on-air, or request basic video recording to the organizers of the event.