What the M in M. Bison stands for
December 13 2011.
Short answer: Mike.
Long answer: Mike is a consequence of a three character name switch for the North American version of Street Fighter II.
In the original Japanese version, Mike Bison was the Mike Tyson looking boxer with a Las Vegas home level and Don King in the background. Subtle, Capcom.
Balrog, a handsome Spanish name (not really Spanish, nor handsome), was assigned to the masked and unfairly clawed prettyboy fighting in an Andalucian flamenco bar.
And Vega, the final boss, was named after the fifth brightest and "arguably the next most important star in the sky after the Sun." While that rationale isn't far off from naming a villain after the second tallest tree (Stratosphere Giant) or the fifth fastest train (SNCF TGV Sud-Est), I guess "Vega" rings better name than "Sun".
Sagat kept his name. No one in good conscience would change their name to Sagat.
So why did Capcom switch the names for the North American version? I think it was to protect Capcom employees from any or all of: