It would seem that, despite the game's manual claiming that multiple accounts can be created per copy, Spore's DRM actually forbids it:
EA's DRM spyware on the long-awaited game Spore turns out to have an added side-effect: if you live in a household with multiple players, you all have to share the same account. The game's manual says otherwise, but after repeated queries on the EA forum, a company spokesperson confirmed this.
That's right—if you're in a household with several potential Spore players, and you want each of them to have their own account, you will have to buy multiple copies of the game.
Oh dear, oh dear. According to an Electronic Arts rep, page 52 of Spore's manual actually contains a "misprint" where it states that multiple accounts can be created. Quite the misprint. Considering that multiple accounts per game is a very standard practice, this looks incredibly shoddy. A DS game couldn't have the capacity to store three times as many accounts as a PC game. This level of forced control over one's gameplay experience is, quite frankly, despicable.
EA, will you ever learn?