Co-Founder of TBT
http://www.andriasang.com/e/blog/2010/06/17/3ds_software_install/According to Nikkei, gamers will be able copy 3DS software to internal memory. Multiple games can be stored with the system in this fashion. You'll be able to switch between games by selecting a title from the system's main menu.
The paper notes that due to this feature, there'll be no need to swap cartridges. When outside of the home, you won't need to carry game cartridges with you.
Nikkei is a financial paper, so it obviously didn't get into the specifics on how this installation system will work. We'll have to wait for Nintendo to provide clarification.
3DS > Wii confirmed?