In fact, I predict that national governments are going to have to get on board with electronic currencies if they don't want to unwittingly transfer control over their own economies from their national treasuries to a private company.
Indications are that this won't be pegged to USD, but rather to a basket of international currencies. Since there are so many ways to combine a basket of currencies into a single value, this gives Facebook plenty of leeway as to how to price this currency.
Essentially, this is the equivalent of the virtual Facebook nation-state establishing their own federal reserve. More importantly, they've already got buy-in from the major non-governmental players. This will essentially create, all at once, a settlement layer that not only bypasses any individual national government, but also the established banking channels like SWIFT.
The US dollar is the predominant international reserve currency at the moment, and the US government leverages that as a pretty big club via SWIFT injunctions.
If there is an alternative that is ostensibly neutral from a governance perspective, and publicly auditable to prevent arbitrary adjustments/freezes, I could see that being very attractive to countries with a less-than-friendly relationship with the US. We already see rumblings to this effect in US-unfriendly countries:
Of course, since Facebook is based in the US, it also provides the US government with a nice, local target for legal leverage. But it would also be very easy for Facebook to spin off this as a subsidiary and place it somewhere out of reach, like Switzerland. Perhaps they could call it something like Libra Networks? Wait, that sounds familiar...
It would be very difficult to outlaw transactions in a currency when those transactions can be initiated and validated on a blockchain directly by the participants. You'd have to play the whack-a-mole game with access to the chain itself, because with direct validation, you're essentially trying to outlaw barter. Look at the efficacy of the cryptocurrency ban in Venezuela as an example.
Facebook is currently doing an end-run to create the first supranational currency, and it's billion+ users combined with the technological agility (specifically, the lack thereof) of national governments means that they actually have some chance to succeed.
That leaves me really at unease. The Federal Reserve has plenty of its own problems, but it has a history of providing US currency stability.
I doubt an individual foregoing usage of this coin will make much difference in its adoption. Maybe the stability of the US Dollar will still reign superior to this? Paper dollars have their own transaction costs, but come with a lot of nice "enterprise" features I'd like to see in a currency.
There are good things to be said for disruption, but it strikes me as reckless to set out to disrupt the global monetary system, even with the best of intentions.
I'm sure those involved will be making all sorts of assurances as to how everything will be careful, but with a system that's as complex as the global economy it is hubris to think one can accurately predict the impact of this sort of a change.
I don't think it's too far-fetched to imagine a scenario in which adoption of FaceBucks has a not-insignificant impact on some of the world's smaller economies, to whose populations it will no doubt prove useful.
This would change those countries' economic behaviour, and in turn the behaviour of everyone they deal with, rippling through until it also affects those currencies FaceBucks are pegged to.
I don't see such a scenario ending well.