the bitcoin network is really controlled by the economic majority. Thats kind of what cant be evil is about, an attempt to replicate that type of thinking into a corporate structure to fail-safe it. Not even miners can fork the protocol if no full nodes nor users like the change.
You are aware of the Eyal and Sirer paper on this, right? As I understant, a majority coalition of miners
can force users to change the protocol, by sabotaging the "orthodox" chain. Then it would be in the interest of uses and any "orthodox" miners to upgrade to the protocol chosen by the cartel.
They can only force soft-forks, hard-forks are ignored by full-nodes and clients. An attempted forced-hard fork results in hostile miners forming an alt-coin with no users. The limiting factor is soft-forks are quite flexible and can do a lot, some of which could be undesirable.
If the change is minor (e.g., "postpone the next reward halving to 2018"), most bitcoin users will not mind. Only ideological purists will be upset, but all they could do is create yet another fork, with a PoW that cannot be mined by the current equipment. But then no orthodox miners could mine this new "true bitcoin reborn" chain either, so it would start out with a minuscule CPU-based network.
the nuclear big-red-button option of tweaking the PoW hash is a meta threat to miners that they dont quite have the upper hand - if they abuse it, or get too crazily centralised - people would worst case be willing to push it.
Probably thats a MAD argument that keeps miners somewhat sensible as if that button is pushed they are sitting on $500m of scrap electronics with a low scrap parts salvage value.
outside of some disagreement that sidechains create more risk than they remove (I say they remove risk, because bitcoin is exposed to offchain risk & monetary shocks from eg mtgoxings, such that sidechains are a clear improvement over offchain economically)
What would prevent a sidechain from being a scam? Sidechains will not be cleared, audited, or reulated, by Blockstream or anyone else. Their protocols cannot be constrained in any significant way, without destroying their presumed merits. Or is there anything in the whitepaper and other literature that I have missed?
Outside of spam limits which could be protocol enforced, its caveat emptor, you shouldnt put money into a chain unless there is some assurance that security & bitcoin protocol knowledgeable people have audited it. People could certify chains (like sign them - "my name is blah and I'm a security researcher with reputation and I and my buddies audited this code and its good") or wallets could etc. Its good and a feature that people can opt to use uncertified chains. You want a situation where there is real open possibility for technical innovation & competition in chain features.
You also want no central control so no chains can get black listed.
Adam