Okay, I think I have identified a central reason why we disagree on some of this stuff, and it basically stems from views on art criticism.
The phrase "personal preference" to me makes a case for relativism:
"If I think something is good, then it is good."
WRONG.
As Bruce Sterling and others have argued, just because you like something [or just because you can make something, like a mash-up] doesn't mean it's good.
I don't have time to parse this much more right now, but the fact is that it behooves technologists to develop a robust art criticism within these applications.
Another reason I am high on the idea of people making decisions about what to listen to vs. algorithms [if there has to be a choice] is that, while there is a LOT of choice in the music world, it's not even CLOSE to infinite.
I believe that among the 10,000-50,000 (a pretty random number of people i picked), "legit" (whatever that means) music aficionados could parse out the vast majority of great music in all genre/mood/styles, from Britney to Bach, in a fairly short amount of time.
Also, this paragraph:
"You are right when you say that compilations like "Ibiza Club" or "Ellington for Lovers" make a lot of money: so does selling Muzak (the background music in supermarkets and most commercial spaces with music). Background music is the ultimate "genre" that is compatible with group preferences: no one is offended... but at the same time, nobody really cares."
Is utter bullshit. Do you honestly think I'm thinking of it that way?
Finally, let the record show that in all my hundreds of hours listening to last.fm and Pandora [PURELY for research reasons] I have NEVER EVER heard anything that I wasn't already aware of that was half decent. EVER.
So, my perspective on this is skewed. Like everything else, 95% of people don't know shit about music, so these incremental algorithmic solutions are a panacea to them.
Your idea of weighing "influential" people heavier in an algorithm has a lot of merit. I just think that pure human-powered peer production would get to the solution of better music for every occasion a lot faster.