Irreversible transactions make Bitcoin security a high-stakes business.
Timothy B. Lee
2012-09-05
http://arstechnica.com/tech-policy/2012/09/hacker-steals-250k-in-bitcoins-from-online-exchange-bitfloor/
The future of the up-and-coming Bitcoin exchange Bitfloor was thrown into question Tuesday when the company's founder reported that someone had compromised his servers and made off with about 24,000 Bitcoins, worth almost a quarter-million dollars
...
But at least until these new techniques mature, it's wise not to entrust large amounts of Bitcoins to third-party services, even those with excellent reputations. And always encrypt your Bitcoin wallet as soon as you're done using it.