Bitcoin's blockchain configuration controlled effectively by three companies
This article highlights how a small number of entities may be able to exert control of the Bitcoin system, through their control of the Bitcoin mining process. Indeed, the three largest of these companies combined would have a market share of 51%. This  would allow these companies to re-write the blockchain's configuration in whatever way they saw fit. The 21 biggest Bitcoin-mining companies can be found at the linked webpage.
The race is on. Alexander Hassenstein/Getty Images

Flashy startups like Coinbase, Circle, Blockchain, and BitPay are some of the most famous companies in bitcoin.

But arguably more important are the miners — individuals and organisations who form the core backbone of bitcoin, ensuring the digital currency's integrity.

Bitcoin runs on a blockchain, a decentralised and public ledger of every transaction made on the network. By offering processing power towards this, users get a chance to win bitcoin — creating an arms race of miners scrambling to assemble ever-more sophisticated and powerful equipment to "mine" new bitcoin.

This decentralisation has huge benefits, but also comes with new risks: Right now, if just the top three organisations joined forces they would control 51% of the network — giving them the power to rewrite the blockchain as they see fit.

Some individuals go it alone; others join open "pools" where they combine their resources to improve their odds; some larger companies also have mining efforts. While the #1 spot can change from week to week, we have ranked the biggest mining companies using data covering August 5 to August 12 from bitcoin network analysis company Blocktrail.