A simple analysis of who the advertisers are can show that this strategy is extremely unwise. About 10% of all internet users use Firefox, which is not supported. Those numbers apply just to the general public; people advertising with search engines are usually more advanced computer users and so the numbers of people running Linux and/or using Firefox increases dramatically. That means that thousands of users will not be able to access their adCenter account from their favorite work environment.
This is definitely something Microsoft has to re-consider. Despite the fact that they are the makers of Windows and Internet Explorer, their obvious discriminatory tactics might alienate a lot of potential advertisers.