If you're shifting to a demand-driven system, then pieces aren't needed equally. A numerically even piece distribution isn't what the swarm most needs. Indeed, I start watching things on Netflix that I never finish, so having more people with early pieces of something would better mirror actual demand for them.

I'm sure that plenty of people in the Bittorrent community are worried about change, but plenty of people in every community are worried about change. Until I see some math or some simulations demonstrating that this can't work, I won't be persuaded that there's an actual problem beyond the (reasonable and legitimate) fear of change.