No, I don't have a demonstration since nothing like this was ever widely adopted, but it is an opinion shared among the bittorrent community:
"One of the key algorithms in bittorrent is the rarest-first piece picker. It is vital to bittorrent’s performance that the piece picker fulfills both of these requirements:
The rarest piece is picked (from the client’s point of view of the swarm)
If two or more pieces have the same rarity, pick one of them at random
The reason to pick a random rarest piece is to always strive towards evening out the piece distribution in the swarm. Having an even piece distribution improves peers’ ability to trade pieces and improves the swarm’s tolerance to peers leaving."
http://blog.libtorrent.org/2011/11/writing-a-fast-piece-pick...
I think that analysis only holds for people who want the whole package and aren't in a hurry.
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.
