As I think more about it, I wonder if companies using player content is a good thing. Now, it can be assumed that eventually every game will have some form of player content, as players tend to modify games, make maps, etc. However, relying on player content for a majority of gameplay is a huge mistake that I feel looming on the horizon.
Let's look at a possible scenario. Big Game Company Inc. decides that instead of spending a lot of money developing content and unique characters, they will just make copies of player's characters and use models very similar to them in skills and appearance as NPCs. This saves countless hours of NPC design and customization. The downside to this? Well, that's quit simple.
You see, if you rely on players to make the content, you will either have to filter content to the point that it would be cheaper just to make it in the first place or allow the crap to pour in. Development teams have some standards to which they are help (or they are fired) whereas players playing for fun only report to themselves. I have intentionally created weird or stupid things when playing games and being exceptionally bored. Is it fair to have these boredom-inspired creations ruin someone else's gameplay?
The bottom line is that player based content should be an addition to games, not a central aspect. I question how well SPORE will do, and how effective the player content system will be with that game.