According to the RIAJ Yearbook 2010, mobile music sales for 2009 in Japan tipped the scales at almost $1Billion usd. http://bit.ly/hHnuUg
A recent article in the local press, focused mainly on PC, prompted us to dig for an official update from RIAJ – Recording Industry Assoc. Japan – on the current mobile music scene. Low and behold they have kindly published [.PDF Here] the most recent fiscal year numbers, for 2009, in English.