Keywords/phrases: Alternative consensus mechanisms/ algorithms are a new science, started in January 2009. The number of academic papers and PhD dissertations focused on consensus algorithms is increasing. This is not a theoretical science, this is an experimental science which can be run on a global scale. We need to see large-scale deployments of practical use, with real actors and real money at stake. Different consensus algorithms produce different characteristics and features. Proof-of-work produces thermodynamically guaranteed immutability. This is not a zero-sum game, there is plenty of room for competition and niche applications.