Won't work. Apple has never worked with miniDV tape cameras via the USB port for video import. Currently the only low cost option is to use the AV video out and buy something like the the EyeTV Hybrid device.
Apple (
Steve Jobs) says you are not allowed to do that with your new consumer laptop so tough luck. Your solution is to take that Mac back and buy any other model other than the new Macbook or Macbook Air versions. By the way, Apple still sells one version of the previous Macbook version, but that is large graphics downgrade.
This is a marketing decision that is going to mess with many people like your self. Several threads discussing this topic have shown that many people are upset with this choice. I, like many long time Mac users, have many external drives that are firewire based. I was considering purchasing a Macbook very soon, but the lack of firewire is a no go for me.
There is some small hope. A cable exists that converts USB to Firewire. The problem is that currently there are no drivers to make the process work in OS X. I think it possible that some third party Mac developer will put a package together. The thing is then, why hasn't someone already done that for USB tape cameras.