Farcaster is a sufficiently decentralized protocol for building social apps. Sufficient decentralization means that two people who want to communicate can always do so. It also means developers have permissionless access to public data on the network.There are five main building blocks in the protocol:Accounts, which represent users on the networkUsernames, which point to accountsSigners, which post messages on an account's behalfMessages, which represent public updates by accountsStorage, which must be rented by accounts to publish messages