Economies of scale are an important concept in Proof of Work (PoW) mining.
Recently multiple cryptocurrencies have faced increasing risks of a so-called 51 percent attack.
Proof of Work mining, such as implemented for Bitcoin, Litecoin and Dogecoin, is an extremely competitive process by nature.
Coin age is a central concept in Proof of Stake (PoS) algorithms. Both PoS and Proof of Stake Velocity (PoSV) are alternatives to the traditional Proof of Work (PoW) mining.