Jimmy Song, author of Programming Bitcoin, discusses the importance of more miners participating directly in the peer-to-peer network and the risks of bitcoin mining pool centralization, including how centralization in mining pools could enable censorship of bitcoin transactions and how it might also enable changes to the network’s rules that would otherwise be far more difficult, ranging from scenarios that cover mempool policy (e.g. OP Return filter) as well as consensus changes, in both softfork and hardfork scenarios.