As has been mentioned if you have nothing to hide whats the problem? 'They' may get more info on you...... does it matter? What is the worst 'they' going to do with you biometric details? Print out a list of travel movements?
There are bigger fish to fry than the paraniod.
I think a couple of white domes currently sitting at the top of the south island will be invading more of your privacy than a fingerprint across the border.
Besides whats the alternative? Take the risk of illegal immigrants so that the rest of us dont loose our warm fuzzy feeling? Not taking a dig at anyone but its exactly that sort of naivety about the bigger world that has made NZ the PC joke it is.