Put teen girls and teen boys together in a virtual world setting and the first thing that happens is they start hooking up. I freely admit I was taken by surprise by the pervasiveness of this culture of virtual boyfriend/girlfriends. In ourWorld, you can enter any room at any time and there will probably be at least one person puttin' the virtual moves on another person (or more.) Some people seem to take this 'dating simulation' very seriously, while others quickly dismiss the 'dating' as nothing more than play-acting.
I'll tell you this much, the fighting over spurned virtual love seems sincere enough.
To what extent should this sort of thing be discouraged, tolerated, or promoted?
The only wrong answer is to merely tolerate the practice (the default response.)
If it's discouraged, you simply say "no dating" and be done with it. At first we were amused when we noticed Dizzywood.com had "no dating" in it's code of conduct. A few weeks later, I see exactly why it's there. I'm sure they're serious about enforcing the rule, too. This is ideal for sites aimed at younger kids. For the most part they aren't interested in dating, and the rule clarifies not only what is allowed, but makes it clear WHO is supposed to be on the site.
What about promoting dating? My concern (and parents, I'm sure) is that the dating sometimes turns into cyber-sex. I think providing dating 'tools' that are in-bounds taste and age-appropriate-wise, you'll minimize your users' desire to go beyond those bounds. If your users are interested in dating, let them date. Let the date system be fun, engaging, one-on-one, and end with a virtual kiss at the door (rather than a chat log that makes me want to wash off the ick with brillo pad.)
Either prevent it or shape it. Half-hearted strategies will provide a sub-optimal result.
Oh, and kids, don't type anything you don't want a fat 38 year old gamer nerd reading. (I wish I could get that message to every teenager in the world.)