Presumably Bluesky's social media protocol will need to operate on some data/ledger structure, to maintain a large social graph (follower/follows), user records

Presumably Bluesky's social media protocol will need to operate on some data/ledger structure, to maintain a large social graph (follower/follows), user records (public key hashes, posts, etc). If too few nodes are hosting this data, it would be malleable to manipulation by the hosts. The same occurs in blockchains that are not widely distributed enough: a blockchain with 5 validators (hosts) is more susceptible to manipulation (i.e. hosts changing records/data for their own gain) than a blockchain with 50K validators, because the cost to control the network becomes exponentially expensive. Strong cryptography has nothing to do with this, and does not prevent this kind of manipulation. Imagine a sort of 51% attack on Bluesky's social graph, in order to manipulate a user's associated public key hash or alter the social graph for some nefarious reason. A blockchain ledger probably is not the only solution, but it does create a strong financial barrier to manipulation (i.e. 51% attacking a widely-distributed PoS blockchain ledger would be prohibitively expensive and short-lived). I am interested if Bluesky is considering these problems and whether they have alternative non-crypto/blockchain solutions.