GameCyte has an excerpt from that conference call where EA CEO John Riccitiello suggests that a best case scenario for Spore will eventually include microtransactions:

Yes, we’ve got a clear, obvious and very compelling post-launch monetization opportunity. This is a game where basically, the parts are what make the sum of the product work. So selling parts as we do with the Sims Store online right now in The Sims 2 is incredibly obvious, we have all the technology for it, but that’s really not what the overwhelming portion of our focus is on right now. It’s on making that a successful launch and making sure we have the right to ask that question down the road.