** For that reason, the cartel can define and change its terms of service, and not even a supermajority of the users can stop them;
That is the crux of your argument and it is so simply not true on many levels.
It is the P2P node network which validates and protects the integrity of the network, not miners. The miners only determine _ordering_ of transactions on the blockchain. That is how the system works.
This argument is superficial and flawed. The users can reject unorthodox blocks, but cannot create orthodox ones; whereas the mining cartel can block the orthodox chain while keeping their unorthodox chain open and functional. So the users cannot oppose the miners, nor interfere with their operation. Each user has only three options: (1) stop using the bitcoin system and lose all his coins, (2) upgrade to the cartel's revised protocol and continue use the full network, or (3) upgrade to some 'rebel' protocol which is run by a tiny CPU/GPU network. (He can opt for both (2) and (3) at the same time, or switch between them any time; but then he will risk committing or be victim of double-spending.)
Please do read the detailed "script" that I posted to reddit:
http://www.reddit.com/r/Bitcoin/comments/2qdfat/without_downvoting_me_to_hell_can_someone_explain/cn5s41zhttp://www.reddit.com/r/Bitcoin/comments/2qmfgw/so_warren_buffet_says_bitcoin_is_bs/cn82t3qhttp://www.reddit.com/r/Bitcoin/comments/2qmfgw/so_warren_buffet_says_bitcoin_is_bs/cn7rxz1