This week's halt, and possible collapse, of the Mt. Gox exchange may or may not prove to be the beginning of the end for Bitcoin - but to borrow Winston Churchill's phrase, it is certainly the end of the beginning.
Mt. Gox had already lost its place as the leading Bitcoin exchange before the murky chain of events that led the Tokyo-based site to shut down. An apparently leaked internal document indicates that the site may have been the victim of a major theft, in which perhaps more than $300 million worth of Bitcoin "disappeared" from the exchange's accounts. I put "disappeared" in quotes because, of course, Bitcoin has no physical manifestation.