Zero Confirmation Transactions are no longer science-fiction

The very basis of bitcoin transactions – the blockchain – has always relied on miner confirmations to determine whether a bitcoin transfer was indeed valid. For most bitcoin users, confirmations are essential to prevent double-spending, a scam where one bitcoin is spent at two different places at the same time. For the most part, this verification system is highly reliable, and usually 6 confirmations guarantee that a transaction was indeed valid. While verification was not so much o