The Rock Band Network - a downloadable store where musicians could independently convert their music and put it up for sale - is being stopped on the Wii, due to the "smaller online install base and limited demand". Apparently, it took a significant amount of time and work for the Harmonix audio team to convert and process the tracks, and the relatively limited demand forĀ releasesĀ on the Wii means that it wasn't cost-effective.
The standard song downloads are not affected - the one's by more popular, and Harmonix-approved bands - will still be available. As far as we're aware, the Rock Band Network on the Xbox 360 will remain unaffected, which does make you wonder what additional cost there is in making the same Rock Band Network songs available on the Wii...