The Ethereum ecosystem — the most important commercial network in crypto, handling billions of dollars worth of tokens — is getting increasingly centralized.

On Sept. 27, blockchain infrastructure provider Blocknative said it will stop operating as a so-called relay, a key participant in adding blocks of transactions to the Ethereum blockchain. Its exit leaves only four other major relay players to handle most Ethereum blocks and raises concern of potential problems, ranging from the censorship of transactions to stealing of other key operators’ profits.