The full answer, however, depends on what you think the best long-term strategy is for capturing and retaining new users. The way I see it, ignorant, unsophisticated, new users don't stay ignorant, unsophisticated, or new. They get some experience, and they want more. As a browser, the inevitable reality is that users will surf, and read, and learn. They will figure out their own preferences and start choosing them.
People like to customize their browsers.
It's their online vehicle, and it should feel like home, not somebody else's property. MSN Explorer isn't, and although this strategy of inflexibility will certainly scoop up some users and steal others, long-term dominance isn't possible over a population that naturally desires freedom, and the ability to own their experience. If so, Microsoft will give up the future new users that continued inflexibility would have acquired. With flexibility, the walls come down. Microsoft has failed to bring the battle to its strong ground of software.