I think the issue with Youtube is that, in general, those who comment are either young kids with a tiny bit of knowledge who don't yet respect the freedom that anonymity gives them, or people who go on there with a few keywords in mind to punch into the search engine (on their chosen subject), with a mission statement of spreading their 'superior' knowledge all over the domain in an attempt to be the best armchair specialist out there.
and put that together with the Iphone generation and you get lots of bits of diatribe in small doses instead of a smaller number of bits of diatribe in large doses
That's the problem with running a "blog". The comments are nearly all banal, because of the way the system works and because of the audience that is willing to comment being largely of a specific type and having only a limited capacity for writing even if they wanted to say more (Iphone users). That's why I don't do my trip writeups using blogging software.
The only times I recall Youtube comments being worth reading were where somebody posted a video of some 1960s band, and one of the members comes on and tells what he is doing now and what great times he had then