There is an article from Business Week on 101Tokyo 2008 that pretty much agrees with what Meg said - Japanese art fans are not necessarily Japanese art collectors.
Eye on Asia Tokyo Art Fair Revisited - BusinessWeek
There is also a nice report on the 101 Tokyo art fair, with a lot of pictures, at Ping Magazine:
Tokyo 101 Art Fair Review - PingMag
Maybe Art Fair Tokyo and 101Tokyo will help to create more Japanese art collectors in the future.