Bitcoin, a faddish, alternative currency that briefly attracted claims to being "one of the top-returning assets of any kind" (according to Dow Jones) has taken a fall.Online news sites FT Alphaville and Finextra both feature accounts - and a chronology - outlining the decline of the exchange rate of Bitcoin against the US dollar, to US$17.5 cents, which happened within minutes over the weekend on Mt Gox, one exchange used by enthusiasts of this "peer-to-peer currency".The episode, as well as other issues around this elusive store of value, has lost Bitcoin a champion. The Electronic Frontier Foundation yesterday removed Bitcoin as a payments option for donations.