With regard to putting money in New Zealand Dollars, it is definitely a risky proposition at the minute (unless you plan on living or working in New Zealand)

In the financial world there is something called the 'carry trade' which is the practice of borrowing money in a country/currency with low interest rates (today the Japanese Yen or Swiss Franc) and depositing it in a higher interest bearing currency such as the New Zealand Dollar (or GB pound for that matter).

The entire global financial system has been doing just this for the past few years and this massive flood of money into the New Zealand Dollar and for that matter the GB pound has been pushing the value of these currencies up, which has made the 'carry trade' even more profitable, since the value of debt devalued and the deposit appreciated relative to each other.

However this whole phenomenon has an element of a speculative bubble. The entire global financial system has placed huge bets on the carry trade and has thus far made handsome profits which it has used to drive up all manner of other asset prices. However, any major shock event could and probably would cause a massive stampede out of the carry trade (ie. a massive exodus out of currencies like the New Zealand Dollar and therefore a massive depreciation of these currencies).

This actually did happen in 1998. The Russian government defaulted on its external debt and this caused financial contagion, ie, widespead panic in the financial markets, leading to a massive stampede out of the carry trade. The US Dollar and GB Pound both lost more than 20% of their value against the Japanese Yen (which back then was also the major funding currency for the carry trade) in a matter of weeks. This caused major financial carnage and lead to the collapse of the celebrated LTCM hedge fund.

Only in the past few days, there have been reports of financial distress at investment funds linked to US sub-prime (ie. low end) mortgage lending market which a few people are saying could be the final trigger for the reversal of the carry trade, although it is utterly impossible to say whether it actually will be or not.

It is possible that New Zealand Dollars could keep climbing and the carry trade keeps chugging along and continues to make money for anyone depositing their money in New Zealand Dollars. But be weary. It could reverse at any time and blow up in your face at any point. And nobody really knows when and where that will be.