For small countries, bitcoin is a big threat. But for big countries like the US, btc has little impact on the legal tender. So I think there is little policy risk in a short run.
This is a valid point. The float of bitcoin already has surpassed the M0 money supply of many smaller nations ...
https://bitcointalk.org/index.php?topic=154954.0If I was a central banker for a "Parity Watch" country I would be considering either adopting parallel currency tender laws to encourage bitcoin circulation or banning it altogether (whilst recognising ultimate futility)
... do you see anybody lining up to buy Burkina Faso Burkinabe CFA Francs before bitcoins?