EA have finished their work on a first iteration on the road to fixing the “only one screen name per Spore install” issue. Caryl Shaw reports on the official Spore Forums:

You can now set up multiple screen names for your Spore account.Log in to spore.com and go to your profile page. At the top of the page you will see a link that says Manage Spore Screen Names. That page has an FAQ about the new system.

Keep in mind, this is just a first iteration of this feature. We hope to continue to improve it and I will keep an eye on the Sporum for feature requests and bugs. We apologize for not being able to solve all of the problems with this system – but Spore was originally designed from the ground up to only support a single player.Regarding Achievements: In the original post on this board, I stated how we thought Achievements would work. It did not end up working that way.

In this first pass, any achievement you get from this point on will be awarded to all the screen names attached to the Master Account. If you play for 100 hours and get the Spore Addict achievement, it will also show up on your little brother’s profile page, even if he’s only played for one hour. Any achievements you’ve earned before now will only show up on your original screen name’s profile page.

We know that this is not an ideal solution and will work on improvements to this in the future.

Too bad they haven’t been able to get the Achievements right yet, but it’s good multiple people in one household will now be able to share their content under their own names!