::::I'm mystified as to how some people keep claiming that M is more common than B. In what country and among what kind of people? Most people in English-speaking countries outside of Asia have no idea where M is and many don't even know what it is. Most people do however know that B is a country, and almost all of these know that it's somewhere in Asia. And since most people in English-speaking countries had and have only a vague idea where Burma is, the change in the official name only confused them more. It takes much longer than 18 years (1989-2007) for a new name to become common in general use, especially if the old name is used extensively in both the media (at almost every first mention of M) and general speech when (rarely) speaking about it. Even those news outlets that mindlessly use M instead of what their customers understand and what the elected Burmese government (so-called opposition) wants show demonstrators saying mostly B and with signs using mostly B. 
 ::::So far i've been speaking about what normal people understand and hear. I hope you're not seriously going to claim that more normal people in English-speaking countries (except perhaps in Asia) will actually use M in talking to others?! They would be afraid of sounding snobby or of not being understood and they don't even know how to say it, which is the main reason why they don't use it. Even highly educated people are confused, as shown by the many different pronunciations listed in dictionaries. This is proof that M only exists on paper and in the news. It is not yet really an English word. Most people have trouble understanding that writing is a tool, not a separate language. When a written word does not have only a few pronunciation variants, that is clear proof that the word is not yet part of the spoken, "real" language. As soon as a word is used often, only a few pronunciation variants survive. 
 ::::In addition, use in scholarly, academic, and expert writing strongly favors B, as clearly shown here. The use of M in the media is simply mindless adoption of official Burmese and UN use, which is dictated by the wishes of the rulers of its member states, which can include crazy generals using unscientific transcriptions to promote their agenda. In addition, we all know that an excellent broadcasting company like the BBC makes its own decisions whereas most newspapers and other media mindlessly follow some style guide like the AP's, so the use of statistics to show how common some term is is OK (and scientific, i.e. linguistically correct, when done correctly) when dealing with use in normal English by the general public and on reputable websites and in other expert and general scholarly sources, but it is not a valid linguistic argument in discussing media use.