Adam Turner worries about public Wi-Fi security at the the Sydney Morning Herald in Do you trust public Wi-Fi?.:
Free Wi-Fi is almost everywhere, but why risk it when you can stick with mobile broadband?
Turner's point is it doesn't make sense to use what might be insecure Wi-Fi networks when most people have plenty of mobile data on their phone plans.
I'd certainly avoid using unknown free Wi-Fi networks, they are too risky. But what about Telecom NZ's network or Tomizone? Are these more secure or is that an illusion and how much safer are the mobile networks? If you can shed light on these questions please use the comments.