bradstewart:

30Gb is actually heavy use, the vast majority of people would use 10Gb or less. The heavy users are the ones ruin for others, see the Woosh unlimited issues where some (in my opinion selfish) customers were using well in excess of 200GB

I don't believe this, I believe it is the ISP's which ruin it for the users by believing that they can offer flat rate plans at cut rate prices and then realise they can't and pull the plug. It's happened time and again in the NZ telco marketplace, but every ISP trys to have a go, realises human nature is what is it and pulls the uneconomical plug. 

Any product or service you offer flat rate on people end up using a lot of, it's to be expected. Look at flat rate toll calls around NZ, Go Large, flat rate dialup, buffet dinners, free refills, water.