Viral launch page secrets

I'm the co-founder of a social startup and we're now building out our launch page. When complete, our launch page will contain a composition of imagery and video. Visitors that signing up will get (1) early access to our beta application and (2) the opportunity to claim their username on our platform after referring 5 friends. They will easily be able to share the page with friends via email, Facebook, or twitter.

Have you developed launch pages that have generated significant traffic in a short period of time?

It would help to get some input from others who have developed successful pages. In your response, please tell me the technique(s) you used and how many signups you've receive in what time period. Also, including information about why you think it worked or didn't work would be helpful.

Thanks in advance.