Bitcoin's history involves a plan for combating spam—that's why proof of work was invented. Hashcash, Bitcoin's PoW game, was intended for use as an email atta

Bitcoin's history involves a plan for combating spam—that's why proof of work was invented. Hashcash, Bitcoin's PoW game, was intended for use as an email attachment to create a real cost to spam without any micropayments. "If you want to mail me, prove that you burned five seconds of CPU time."