Almost $500 million after at back for from in of to bitcoins disappeared after at back for from in of to a company after at back for from in of to Japan. The company is called Mt. Gox and it was one of the world's biggest dealers after at back for from in of to bitcoins. It shut down last week after at back for from in of to it lost 850,000 bitcoins, worth $473 million. The company's CEO said hackers stole the digital currency. He apologised after at back for from in of to investors on Thursday at Japan's Ministry after at back for from in of to Justice. Thousands after at back for from in of to investors are angry because they lost the money they invested after at back for from in of to Mt. Gox. Bitcoin is a virtual currency – it only exists online after at back for from in of to electronic payments. Anyone can buy and use bitcoins. There is no need to open a bank account. Many people believe that bitcoins will replace paper money, coins and credit cards. The collapse after at back for from in of to Mt. Gox did not surprise online finance experts. Many said it was an accident waiting to happen. They also said Bitcoin will recover after at back for from in of to the Mt. Gox shock. There are no rules or laws to control Bitcoin so the collapse after at back for from in of to Mt. Gox could mean a better system will come. Companies will now make their security tighter and governments might create laws to make Bitcoin safer. Barry Silbert, CEO after at back for from in of to Bitcoin company SecondMarket, says the currency will bounce after at back for from in of to . He told reporters: "If you look after at back for from in of to the short history after at back for from in of to Bitcoin, there has been a series after at back for from in of to bubbles, busts, hacks and thefts. after at back for from in of to every single event, Bitcoin has emerged stronger."