????2013年，比特幣的表現繼續讓人大開眼界，就算11月末它開始大跌之后，仍然精彩不減——如果按照12月18日530美元的價格，在1月份以13美元買入的比特幣回報率超過了4,000%。比特幣價格飆升還引爆了另一輪熱潮：今年先后涌現出100多種“替代幣”，它們都是各種社區模仿比特幣用代碼攢出來的，名字也千奇百怪，比如什么Nova幣、Zeta幣、Bitbar、Cryptogenic Bullion、BBQ幣，哦對了，還有Sex幣。其中有些對比特幣的技術做了小幅、有意義的改進，但多數都是赤裸裸的抄襲——很大一部分干脆就是一種詐騙手段，純粹是想利用加密數字貨幣支持者的熱情發筆橫財。

????不過，這些貨幣仍然是比特幣發展史的重要組成部分，其中有一些還可能在未來獲得應用，其中就包括加密數字貨幣，這是一種主要使用加密技術制造的數字貨幣。就算近期由于比特幣價格大跌拖累很多替代幣的價值跟著下挫，還有五種替代幣各自市值均超過一千萬美元，另外20種每種超過一百萬美元，還有一些被恰當地稱為“垃圾幣”的，當前市值也有約75,000美元。安德里亞斯?M. 安托諾坡羅斯是幾個涉及比特幣業務的初創企業的咨詢師。他寫了一本即將出版的比特幣技術專著，也是知名播客“話說比特幣”（Let's Talk Bitcoin）的主持人。他把當前這種情況稱為“加密數字貨幣生態系統”。

????這個生態學比喻與進化邏輯有一部分關系。安托諾坡羅斯稱：“替代幣有兩個目的。首先，它們是用來測試新技術的，看看這些技術是否可行，以及市場是否接受。”這些新技術主要圍繞比特幣挖掘算法的不同形式展開——這種算法是一種“工作量證明”（proof of work，指系統為達到某目標而設置的工作度量方法，最初被應用在網絡的拒絕服務識別和反垃圾郵件上——譯注）的問題解決技術，它能保護流通的貨幣及其交易記錄。這些采用不同技術的貨幣包括：允許一種貨幣由不同于比特幣的設備處理的（Lite幣，目前市值為3.3億美元），聲稱使用能量更少的（Peer幣，市值4700萬美元），以及能提供更快交易確認時間的（這種貨幣有很多，比如市值500萬美元的Feather幣）。其他加密數字貨幣則宣稱使用了更加特殊的技術，比如Frei幣（市值兩百萬美元）內置了滯期費，如果它僅僅持有卻不用于消費的話，就會失去價值。甚至還有一種貨幣用工作量證明算法來尋找新質數（這種貨幣的名字當然就叫Prime幣，現在市值六百萬美元）。安托諾坡羅斯稱，這些技術特性在接受某種替代幣“測試”后如果證明富有吸引力、而且可以實現兼容，它就有希望被納入比特幣的范疇。

????不過似乎沒人認為這些替代幣會取代比特幣，成為一統天下的加密數字貨幣。正如近期美國銀行（Bank of America）的一份報告所指出的，比特幣的統治地位主要是由網絡效應來保障的：它的價值是由超大規模和挖礦群體、服務提供商、用戶及商家所投入的資本賦予的。如果沒有比特幣的規模及網絡的力量，許多替代幣隨著它們依附的網絡被拋棄或被黑客攻破，都會銷聲匿跡——安托諾坡羅斯稱替代幣的第二個目的就在于，“展示觸目驚心的失敗模式”，而它失敗的教訓將使幸存者更加強大。

????Bitcoin's 2013 remains impressive, even after the digital currency has taken a serious tumble since late November – at the December 18th price of $530, a Bitcoin purchased for $13 in January would return over 4,000%. Another explosion has tracked that price's: the emergence this year of 100 or more "altcoins," collections of code and community modeled after bitcoin and with names like Novacoin, Zetacoin, Bitbar, Cryptogenic Bullion, BBQCoin and, yes, Sexcoin. Some offer minor but meaningful variations on bitcoin's technology, while most are outright copies – and a huge proportion are fraud schemes preying on the enthusiasm of cryptocurrency supporters.

????Still, these coins are an important part of the story of bitcoin, and some are likely to be part of any future that includes cryptocurrency, a type of digital currency that depends on cryptography. Even after the recent bitcoin decline took many altcoin valuations down with it, there are five altcoins with market capitalizations of over $10 million each, another 20 of over $1 million each, and dozens of others ranging down to the aptly named "junkcoin," with a current market cap of about $75,000. Andreas M. Antonopoulos, a consultant on several bitcoin-related startup projects, author of a forthcoming technical volume on bitcoin, and host of the popular "Let's Talk Bitcoin" podcast, describes this landscape as the "crypto-currency ecosystem."

????The ecological metaphor hinges in part on an evolutionary logic. "Altcoins serve two purposes," Antonopoulos says. "First, they test new tech features, showing whether they work and whether the market will accept them." Those new features mostly revolve around variations on bitcoin's mining algorithm – the "proof of work" problem-solving that secures a distributed currency and its transaction records. Variations include those allowing a currency to be processed by different equipment than bitcoin (Litecoin, current market cap $330 million), those purporting to use less energy (Peercoin, $47 million), and those that offer faster transaction confirmation times (many, among them Feathercoin, $5 million). Other cryptocoins claim more idiosyncratic variations, such as the demurrage built into Freicoin ($2 million), which loses value if it is held without being spent. There's even a currency that uses its proof-of-work algorithm to search for new prime numbers (that currency is named, of course, Primecoin, $6 million). Those features that prove attractive and compatible after 'testing' by an altcoin, Antonopoulos says, will likely be incorporated into Bitcoin.

????No one seems to foresee any of the altcoins displacing bitcoin as the dominant cryptocurrency. As a recent Bank of America report pointed out, bitcoin's dominance is guaranteed above all by the network effect: the value imparted by the huge size and capital investment of its community of miners, service providers, users, and merchants. Without bitcoin's volume and network strength, many of the altcoins will disappear, as their networks are abandoned or overwhelmed by hackers – Antonopoulos says the second purpose of altcoins is to "demonstrate spectacular failure modes" whose lessons will strengthen the survivors.