WhatJapanThinks, in February 2007:
Q3: When upgrading your mobile, what are the features that are important to you. (Sample size=1,000, multiple answer)
Memory card: 342. Music playback: 199. One Seg (terrestrial digital TV): 195
I was reminded of this survey by Benedict Evans, who sensibly says:
What Japanese consumers thought was important in a phone in 2007 – a good example of the problem of relying on user surveys.
You should subscribe to his weekly newsletter, one of the best when it comes to mobility: ben-evans.com/newsletter