But does China restrict paper fiat transactions? The basic question is whether you can force forfeiture of an innocent receiver of a tainted bill. You can alwa

But does China restrict paper fiat transactions? The basic question is whether you can force forfeiture of an innocent receiver of a tainted bill. You can always legally do this, but it diminishes the utility of the medium--the very purpose of currency, afterall, is to provide an efficient substitute for barter, and the greater the fungibility the greater the efficiency. Is the benefit in suppressing criminal activity worth the cost imposed on economic activity? The more potential innocent, protected receivers, the greater potential for effective money laundering, the less effectively you can suppress illegal activity. The cost is a function of determining provenance at the point of a transaction, and the benefit a function of degree of ubiquity. This cost is most minimal when all transactions already occur electronically, online, and in real-time, as with Bitcoin. Similarly, it's precisely such a system where you can impose the burden most ubiquitously--literally every individual and every transaction subject to your legal authority without very much technical effort. So it's with something like Bitcoin where you're most likely to see heavy reliance on tracing and tainting because shifting the burden onto innocent receivers imposes the least cost to them individually and to the transaction system generally. By contrast, paper fiat is the place you're least likely to see this strictly employed, so long as it remains a substantial medium for exchange. (Rather, the tracing is most useful for catching criminals, not passively diminishing their ability to utilize the transactional system itself.) AFAIU, not only does China have systems in place to more ubiquitously trace bills at certain points in the system, they're also actively encouraging (i.e. forcing) a shift to electronic payment platforms. The details of precisely what they're doing, when, and how I don't know much about. But the basic principles and concepts are clear, making the trajectory of what they need to accomplish easy to predict. Especially in jurisdictions with long established, legally mandated fungibility guarantees regarding paper fiat, many Bitcoin advocates are unwittingly ushering in the future they claim to fear most.