assuming you invest in a currency of country which has a limited supply of money and you can be pretty sure that it will never be changed.
assume further that this country has the possibility to fill some niches in the global economy
you think it is insane to invest in the currency of this country?
If the currency is inflating @ 10% a year, and its dollar exchange rate has fallen by more than 50% in 2014? Let's just say "not very smart."
the dollar exchange rate has increased by around 150 times in the last one and a half years - very smart investment
induction as an indicator over time is stupid.
you can argue that my assumptions are wrong or that the niche is very small but arguing over charts is beyond stupid
if these assumptions are true and the niche is big enough you can say that investing in this "currency" is sane.