ERC-4337: mempools all the way down

This post argues that once ERC-4337 is widely adopted, it will create alternate "user operation" mempools that fragment the public sources of MEV opportunities. It says searchers and builders will likely run bundlers, which are new actors that act as userop relayers and proxies for EOAs, so that functionality may be absorbed into existing roles. The author also suggests that paymasters, which let third parties pay for user operations, could be subsumed by OFAs, and that bundlers may be a trojan horse for bringing alternative mempools to Ethereum.