This could, in principle start a war similar to the ones Microsoft has been fighting for years, although Chrome's faster update system might help Google win. I

This could, in principle start a war similar to the ones Microsoft has been fighting for years, although Chrome's faster update system might help Google win. In principle, given Chrome is often installed as the current user, there is nothing to stop any other user program from changing Chrome in any way it sees fit, simply adding an extension and marking it "user accepted" in whatever way. Microsoft has had trouble with this kind of thing for years, as I say.