Bitcoin has reached an important milestone. The digital currency is renowned, or rather infamous, for its dramatic speculator-driven price surges. Only this week, its value plunged from US$700 to US$540 when a key exchange discovered a software flaw that could allow thieves to withdraw twice the correct amount -- and not that long ago it was up at the US$1200 mark. Well, now bitcoin has been linked to another notorious source of irrational speculation: tulips. Thanks to a start-up flower-seller called BloomNation, you can now buy tulips with bitcoin. We've built the whole thing now, folks. We can all go home. The bitcoin community hates it when the supposedly ever-rising value of their darling digital disruptor is compared with the Dutch tulip mania of 1637, but for those who haven't been drinking the Kool-Aid the parallels are obvious. There's the fact that we're talking about the price of something that has no real value in and of itself -- although that's true of all fiat currencies. There's the almost religious belief that the price will keep on rising. There's the matching claims that any drop in price is just a temporary aberration. There's the wild-eyed enthusiasm of first-time speculators. And now there's the extravagant evolution of varieties and cross-breeds -- an almost Cambrian explosion of digital currencies that's creating a gloriously exploitable dreamscape for speculators and con artists alike. The computer software that supports bitcoin's peer-to-peer transactions is open source, which means that anyone can copy it to create his or her own clone currency -- or tweak it to create something with a slightly different dynamic, depending on your beliefs about monetary theory and inflation versus deflation. As the rather pretty Map of Coins shows, more than 200 of these "altcoins" have evolved since the publication of the original bitcoin paper in 2008, and you can click through to their websites and their program source code.