Mike Hearn is a former Bitcoin developer who played a significant role in the early development of the Bitcoin network. He contributed to various aspects of Bitcoin's technology and was known for his work on Bitcoin XT, a fork of Bitcoin that proposed increasing the block size to improve scalability. Hearn's involvement in the Bitcoin community was influential, particularly in discussions about the network's direction and scalability. However, he eventually left the Bitcoin project, expressing concerns about its future and the direction it was taking. His departure and subsequent comments sparked considerable discussion within the cryptocurrency community.