GHash

• Mining pool that used to control a significant fraction of Bitcoin's hash rate but is now totally defunct. 
• A mining pool that got 51% of the hash power back in 2014. It broke up in multiple pieces as a reaction.
• “In an interview with Caleb Chen of CryptoCoinNews, a spokesman for GHash said the firm had no intention of attacking the network but was unapologetic about the pool's heft in the system. "We understand that the Bitcoin community strongly reacts to GHash.IO’s percentage of the total hash rate," Jeffrey Smith said. "However, we would never do anything to harm the Bitcoin economy; we believe in it. We have invested all our effort, time and money into the development of the Bitcoin economy. We agree that mining should be decentralized, but you cannot blame GHash.IO for being the #1 mining pool."” http://www.businessinsider.com/today-bitcoins-doomsday-scenario-arrived-2014-6?international=true&r=US&IR=T