Why would Apple port their Safari browser to Windows? I know Steve Jobs said that he wants to see if they can gain market share yesterday, but realistically speaking, that’s not going to happen. Safari isn’t even the best browser for OS X, and Windows users who are up for downloading an alternate browser will probably use Firefox. I don’t think that’s really the point, though. The point is to give Web developers fewer excuses to ignore Safari. Being that Safari is not only the default browser for OS X but the only browser for the iPhone, Apple needs to make sure that more applications are Safari-tested. Plus, this seems like the first step toward offering some kind of Safari-based iPhone software development kit that runs on both Windows and OS X.
Simon Willison predicts the unforeseen circumstances.
Do also check out John Gruber’s analysis of the keynote.