I think we agree on the "broad brush" aspects of the problem (in particular that it's really about the specifics here).
Thank you for the example of fashionable materials science lectures, I now agree on that point.
The specifics here are interesting, though, so I'll take it further.
Discounting values for path-dependency has an appealing elegance, but as a general principle it is, I think, unsound. Any value that saturates has such a path-dependence: I enjoy eating, then I become full, then I no longer enjoy eating. I enjoy learning about linear algebra, then I master it, then I no longer enjoy learning about linear algebra. If you appeal to the underlying value of "not being hungry" or "learning new mathematics" then I can equally appeal to "enjoying fashionable music".
That ignores the specific social component of bandwagons, though, which I have already said that I agree with you on.
I just downloaded the latest Radiohead album, and I love it.
Thinking back, I started listening to Radiohead years ago when I found out that some of the cool kids in school were into it. With all the hype about the new album, the status/fashion processors in my brain going to ensure that I enjoy listening to it. I would probably fail a double-blind test with a bunch of imitation bands' fake "new Radiohead albums".
But I'm really enjoying listening to the album, and that doesn't seem like a bad or contradictory thing at all, even in light of the statements above. If, hypothetically, I was enjoying it for purely non-fashion reasons, then presumably that enjoyment could also be traced back though a causal chain to facts about brain development, evolutionary psychology, or whatever. But we would have no problem accepting that enjoyment as A Good Thing since explaining enjoyment does not diminish it. And so it seems in this case.