Recently i was sent an email about a TradeMe auction selling generic/cultural Maori domain names at highly inflated prices.
A Maori web site owner then wrote an article on her web site and emailed her list of contacts promoting the auction and asking that everyone go and purchase their iwi and other generic Maori domain names to protect them. This is the worst possible advise. It only encourages this sort of behaviour.
For a start, the DNC has a disputes procedure in .nz which is fair and reasonably priced. Secondly, there is always the option of registering a similar name, perhaps with a dash in the name or a little more descriptive. For example, taiaha.co.nz may be already taken, but if you have an online taiaha shop then maybe you could register taiaha-shop.co.nz or taiaha in the myriad of other suffixes such as .com, .maori.nz, .net.nz etc.