It's not maturity, it's caution. People are more careful when their real names are attached.

It's also not a good comparison because the set of options is completely different; it's like arguing whether a trout makes fewer programming mistakes than a human. There are no interactive 3D zoophile sex dungeons in Facebook to use your "free will" to avoid. (Facebook app, anyone?)

I agree that John Gabriel's theory is in play. But I'm not suggesting that the people themselves are less mature, just that the net result is that SL is quite apparently more adolescent than FB.

And I think it's a great comparison. Both of these social/entertainment systems were designed to be the way they are. What are the results?

Certainly many people who have tried both and opted to spend many more hours on one than the other. What difference is there in the communities on each, the interests represented on each, and the individuals who use each? Which is better social therapy for the painfully shy? Why hasn't SL had the FB-like mainstream breakthrough they've been expecting?