Currently, the Algorand Foundation manages the official list of relay nodes, to bootstrap a scalable and reliable initial infrastructure backbone.
It is important to stress, however, that anybody with an Algorand account can run a non-relay node and participate in the Algorand consensus protocol (i.e., be a validator).
Moreover, the integrity of the blockchain does not depend on the relay nodes: as long as sufficiently many participation nodes (in terms of stake) behave honestly, the blockchain cannot fork.
Even if all the relays misbehave, the worst that can happen is that the blockchain will slow down or stall.
The Algorand Foundation is researching options for making the decisions on relay nodes in a more decentralized way.