There is no "i" in team. There is one in your new Nintendo handheld. (There's two in "Wii", but I digress.) GoNintendo asked Ninty straight up what's with the I, and got an answer.

Nintendo insists it's not-follow-the-leader of Apple branding "i" on any must-haveable small gadget that exudes 2.0 coolness. Rather:

‚ÄĘ The "i" is symbolic of the subject "I" and its personal aspect.
‚ÄĘ Plus, the addition of two cameras gives the system its own "eye" on things.

"Nintendo hope that the Nintendo DSi becomes more than a game system and more of a personal tool to enrich our daily lives."

GoNintendo says that comes directly from a Nintendo rep.

Nintendo Tells Us What the I in DSi Means [GoNintendo via Cubed3]