- 51% Attack
The ability of someone controlling a majority of a network hash rate to reverse their own transactions as long as they are in control, and prevent new transactions from confirming. When a miner (or miners/mining pool) gain control of more than 50% of the network’s hash rate, it would allow that person to create changes in the network and potentially open up the entire protocol to fraudulent activity. As the number of miners rises, the chances of this happening drastically decrease. Which is why this system imperatively relies on a democracy.