Isn't bitcoin already owned by a mining pool (ownership defined as an entity that can express 51% of the mining power)? Why is anyone even playing with this sys

Isn't bitcoin already owned by a mining pool (ownership defined as an entity that can express 51% of the mining power)? Why is anyone even playing with this system anymore - the growth of the blockchain is controllable by a single entity! Isn't preventing that the whole point?! http://arstechnica.com/business/2014/07/bitcoin-pool-ghash-io-commits-to-40-hashrate-limit-after-its-51-breach/ http://arstechnica.com/business/2014/07/bitcoin-pool-ghash-i... When a protocol depends on the "Evil Bit" being set to 0 to function correctly, that protocol is broken.