I think the big problem that Apple faced with the new Macbook and Macbook Pros was differentiation. In the past, the Macbooks were made with plastic and cheaper components, whereas the Macbook Pros had metal enclosures, better build quality and better components. Now the two of them are very similar in terms of build quality and finish.
The Macbook Pro gives you a bigger screen, better resolution and a better graphics card. But it is also heavier. I bet that a lot of the "pros" were looking lustfully at the new Macbook as a cheaper, lighter option. Contrary to popular belief, pros also like saving money. By removing FireWire from the Macbooks, Apple has drawn a clear dividing line between the two models. I think that it is a slightly cynical move: it will prop up sales of the Macbook Pro at the expense of sales of the Macbook. Personally, I would have liked to see a unified product line of Macbooks: a 13", 15" and 17" with a variety of BTO options. But Apple will have done their homework, and there must be a margin involved with keeping the Macbook and Macbook Pro distinct.
It sucks for me, personally. If the Macbook had FireWire I would have ordered one immediately because my last Macbook died a few weeks ago, but maybe I am not the target demographic? As it stands, I am typing this on a new Acer Aspire One.