Bitcoin and similar technologies may have a significant role to play in the future, and the technology is legitimately elegant and adeptly applies several modern strains of cryptographical research.
The recent speculative runup in the main Bitcoin block chain, however, is insane and entirely unfounded. I can't promise that people buying Bitcoins now will lose money, for no one can easily predict where a bubble will end, but the grandiose claims of most of the people in the official Bitcoin forums are absurd and border on the illegal fraud that is explicitly disclaimed by people like Rezin777. Investors would be well advised not to risk their money here. There are several significant reasons for this:
1. Most of the exchanges between Bitcoin and other currencies are illegal or, at the very least, unlicensed and illegitimate. They likely run afoul of US securities laws and US banking laws. This is not just a pub-style bull session about law; it is the result of a reasoned consideration informed by legal experts, though of course it does not constitute legal advice to you. Speaking generally, though, individual users of these exchanges risk having their assets and accounts frozen, risk running afoul of money-laundering laws, and generally risk losing even more than they put into the system.
2. Related, given that the exchanges are entirely unregulated, they can themselves be manipulating the market. Given that Bitcoin is touted as a distributed currency, it is ironic that there is absolutely no check on "Mt. Gox," the major Bitcoin exchange, through which $200,000/day is (unbelievably) passing.
3. The Bitcoin protocol itself is not robust against denial-of-service and other attacks. Many on the official Bitcoin forums have noticed this, and some have spelled out the attack vector in detail, but in short, a persistent denial-of-service attack that shuts down Bitcoin entirely can be mounted trivially for about $700,000 and can very likely be mounted with more sophistication at a substantially lower cost. Indeed, the Google employee who (in a personal capacity) wrote a Java version of part of the Bitcoin client has recognized publicly that any sophisticated analyst could shut down Bitcoin at will, and he explicitly opposed calls for tests of the system's security by the general public. The system has created the impression of security, but it is not secure. What ARE secure and robust are the ideas behind the protocol; it is likely that something like Bitcoin will survive, in some form, in the future. But the main block chain, in which everyone's presumed "wealth" inheres, is of questionable soundness. (To say that more simply: Bitcoin as an idea might survive, but it is far less likely that your "bitcoins" will.)
4. Given that technological attacks are possible, a corollary is that economic attacks in the style of securities fraud are possible as well. If you can disrupt the network at will, you can easily disrupt the network in a strategic way in order to profit from the disruption's effect on the market. Much unsophisticated analysis of Bitcoin rests on the premise that attacks aren't worthwhile to mount because it would be more profitable, with massive computing resources, to "mine" for Bitcoins, but that entirely neglects (1) the economic motivations that come from market manipulation and (2) ideological, political, regulatory, and commercial competition to the main Bitcoin block chain, which makes attacks relatively more attractive for many parties.
5. To the extent the official Bitcoin forums have informed investors' views of Bitcoin, they have likely misled the public. This is interesting from a legal perspective because it amounts to fraud without the individualized intent of fraud (can a mob "defraud" someone when no individual person in the mob is consciously telling a lie from which he or she expects to profit?), but several features of the official forum stand out immediately to informed readers. These are largely tangents, but they may help paint a more accurate picture of the current users of Bitcoin than the official forums would:
a. While I said at the outset that Bitcoin is legitimately interesting from a technological standpoint, it is not as creative or novel as most of the adopters seem to think. Judging from the official forums, the typical adopter is someone with a modicum, but no more, of technical and theoretical experience. (Perhaps of note: those who are leading the ongoing "development" of Bitcoin are little different; they are not sophisticated or creative technological thinkers, and they struggle even with the details of the present protocol. What this means for an investor is that Bitcoin is not practically resilient even to those attacks to which it might respond in theory, such as a compromise of the hash function it mainly uses or the development of a new "mining" technology that cheapens various attack vectors.) To paint the picture very broadly: these people know how to run Linux, compile programs on it, and maybe write a few lines of code; they can also evaluate at a very general level the claims of a cryptosystem. But all except about five people on the official forums have no specific mathematical or systems training, and so the general discussion and enthusiasm creates the impression in a novice that Bitcoin is far sounder than it is.
b. More obviously, the official forum is filled with disturbing and juvenile, extreme anarchism. Comments like "I reject all systems of human morality and law" are common. Uses of Bitcoin to encourage trading in illegal goods and services are routine; even "assassination markets" are encouraged. Bitcoin as a virtual currency probably does not threaten governments the way that some novices initially imagine upon hearing about the technology, but when the only people buying Bitcoins are (1) engaging in illegal activities, (2) anarchist teenagers who want to promote the technology for ideological reasons, and (3) speculators, sound investors like those in the Fatwallet crowd would be well advised to stay away. To a mainstream community of investors, however, the deranged rants that are commonplace among early Bitcoin adopters are perhaps reason alone to hesitate to adopt the technology.
6. Probably less significantly, but still interestingly, the Bitcoin block chain has now been demonstrated by at least two good analysts to be able to store arbitrary data "steganographically." This means that the Bitcoin block chain can contain arbitrary contraband, so that merely by running the Bitcoin client, you may (at least theoretically) be propagating child pornography, Wikileaks, and other material in the style of Freenet and other distributed storage systems. This is more theoretical than practical at the moment, but it is disconcerting. How popular would VISA cards be if (say) 4% of them contained contraband information encoded in the holograms on the front of the cards?
NOTHING IN THIS MESSAGE CONTAINS INDIVIDUALIZED LEGAL OR INVESTMENT ADVICE. My motives for writing this are a distaste for fraud, even when that fraud is not consciously propagated. As a researcher, I also have privately made proposals that address some of the technical drawbacks of Bitcoin, but I have no vested interest in seeing Bitcoin as a technology either succeed or fail.