Now, when you do actually launch, you're sure to lose a large percentage of those that signed up. Please make sure to provide a mechanism for easy account cancellation, and I wouldn't recommend activating every sign-up without another click of approval from those that did sign-up during the pre-launch phase. The last thing a happily married person wants is for their profile to pop up on a dating site because they didn't know they were signing up for a dating site. But I'm sure you'll get some level of users that convert to active users of the site once you're live if for no other reason than the fact that their info is already in there ... they're single ... and they're curious.
There's really a lot of ways you can go about it though. Maybe a Mechanical Turk task. Or maybe rewards for referrals that actually convert. Just be creative and think of what might convince you to sign up for your own site.