I have thought this should exist for as long as I can remember. I actually wrote a blog post about it 364 days ago (odd coincidences).
Regarding growth, there must be a spin you could put on the share-this-on-facebook process to make it positive/appealing. Off the top of my head: - keep track of relationship status of the users, and if two get in a relationship after joining and liking each other, encourage them to post it. - making something else go viral that mentions likesecret (eg. a radio station posted a photo of a lottery ticket with their logo and said they would split the winnings with sharers. they had over a hundred thousand shares in just a day or two) - somehow taking advantage of any of the college meme pages that are trending these days... they'd hit your target audience big if you could figure out how