Because Stellar’s FBA consensus algorithm does not reward validators nor punish malicious actors, it’s much cheaper to attack the network than a proof of work or proof of stake network. An attacker can spin up an army of cheap validator instances and quickly outnumber the well-behaving validators. Even if the well-behaving validators could blacklist the army of new validators, it would still be hard for new network users to figure out which consortium of validators to trust. The simplest answer of the “consortium with the most validators” is wrong in this instance. As such, Stellar’s consensus algorithm requires a systemic centralization of trust in a core consortium of validators in order to prevent attacks such as a flooding of malicious validators. The algorithm is not open and accessible for everyone to be a validator; in order to be one, you need to have at least one validator in the trust consortium of validators whitelist you.