Excluded from the features list of the new MacBooks, was the fact that they cannot be used for jailbreaking the iPhone or iPod Touch. While it is unclear as to whether this is a hardware feature, or a software modification loaded on the new notebooks (the new MacBooks run a special version of Leopard), Apple is clearly trying to keep its monopoly with the App Store.
Users over at HowardForums and iPodTouchFans are reporting problems running the Pwnage tool on the new aluminum MacBooks, which don’t seem to be able to recognize an iPhone or iPod Touch when it is booted into DFU mode, a vital requirement for jailbreaking. - Gizmodo
So while you can use a modified IPSW file, or even a jailbroken iPhone or iPod Touch, you cannot use Pwnage Tool to create a new IPSW on the new MacBooks. How far this will help Apple in preventing people from jailbreaking, we can’t be sure. It might shoo away technophobes who just wanted to try out jailbreaking, but someone who is determined can very well get the IPSW done on an older Mac or possibly, Windows (he would have to be really determined to go to that extent!).
Whether Apple is the monster here by preventing such an awesome thing as jailbreaking, or are they really looking out for their customers by making sure they don’t slow their iPhones down with the added baggage, is for you to decide.
