This guy references a very very long video about "why you shouldn't use TrueCrypt hidden volumes" - the relevant question and answer is about an hour in (57 mins will do it) - http://www.youtube.com/watch?v=HHoJ9pQ0cn8&t=57m
There's more to this long running debate, but that's the gist of Appelbaum's position.
My take: Plausible deniability gives you the option to defend the fifth, lie, or give up your data, but your confession may never be plausible. Which is better depends on the sensitivity of your data and the willingness of your adversary.
How will giving up the password ensure there isn't 'another' hidden volume?
First, Part 1 is only 1 hour and 17 minutes long (though perhaps it felt much longer to you).
Second, while the subject of TrueCrypt comes up a couple of times in the Q&A period, it's not the main subject of the talk. The talk is about privacy, anonymity, surveillance, and what can be done about them.
I highly recommend watching this video, especially for people who might not be up to date on all the latest privacy-enhancing technology or who might not be very aware of how much digital surveillance there is these days. Even if you do know about these things, it's still interesting to hear an intelligent, articulate presentation about them.
There is no such thing IMO as only 1:17 when referring to a presentation/talk. I tune out after about 10 minutes, 15 or so tops (e.g. for the git imerge discussion).
Anything that is so complicated that it requires that much exposition is something that I will read about or probably not find out at all.