As much as I like the idea, I see one problem (aside from all the programming & hosting hassle):
Eufloria is, in effect, two people: Alex and Rudolf (forgive me if I leave out the music designer here), they’d have to check every user level for “cleanness” and, where necessary, make changes. Also, there’s some chance that they also will be expected to take responsibility for every crash that occurs with a user level, don’t you think so, too?
So, I for one would prefer if they concentrated on real game improvements, even if it’s only to accept the return key for “OK” <wink wink, nudge nudge>
Or think about the world “quality” … Alex & Rudolf would have to create some quality management for these user-submitted levels … some people would be sad because their levels wouldn’t be included, or other people would be disappointed because of too hard/too easy levels, etc., etc.
As it is now it’s all in the responsibility of the user.