Erik Voorhees launches SatoshiDice, a provably fair bitcoin gambling site that used on-chain transactions for every bet. At its peak, SatoshiDice accounted for roughly half of all Bitcoin transactions, sparking debate about blockchain congestion and what constituted legitimate use of block space. The site demonstrated Bitcoin's power as a permissionless payment rail. In July 2013, Voorhees sold SatoshiDice for 126,315 BTC (about $11.5 million at the time), one of the largest bitcoin-denominated acquisitions in history.
Bitcoin Wiki: SatoshiDice