It's a great idea. For anyone who looked at the 30daychallenge you remember they had the opportunity to send to 3 friends the word.
What you will need is simple, and if anyone does this, you can PM my broke-ass for my paypal as a small reward, cuz it will be major for you if you get an invite script sorted that can basically function exactly like a CPA gateway. lol jk. But you could share the invite script with me in exchange for the blueprint here
1: Get content. You need shocking or funny rare things or current blasphemes in the media type stuff that is still tasteful. No 2girl or 1guy tapes. And something they just have to see that will be easy for you to hype them for on the landing page. "Get ready to see..." "But before you watch it you need to tell 3 freinds.
2: You need to do this to include an option to automatically send it as a bulletin on myspace if they don't want to enter any emails. "It's easier and then everyone knows about it".
3: It doesn't just need to be video, but I can't really think of anything else that people would do the tell-a-friend prior-to-accessing-it thing for off of the top of my head. Pictures, perhaps. Whatever you choose needs to really make your day and tickle something memorable in you whether shocking or pleasant. One angle could be to go with a slideshow of good thoughts and do it like "send a prayer before you receive yours..."
Something like that.
These steps aren't really steps, but that's enough to get your motors running. Prayers, Wishes, etc, something that magically grants them something when they watch the video - people will be glad to forward that to three people, and a higher percentage will take the "easy" way out and expose their entire friends list.
My focus is on learning to make legitimately repostable bulletins and stuff like that that are also profitable. Stuff people love to repost. Bored Bulletin Surveys 2.0, if you will. This invite-before thing can be powerful - but it isn't monetized yet. How will you then monetize it? Use the list you get forwarding all of those invites?