[greglockwood]

Kind of reminds me of Dropbox's viral referral program. The spam-ish aspect can get annoying at a point, but the interesting thing is that it's not the website that's spamming you, it's your friends, so you can't really be mad at the website.

This makes me think the viral referral model still has some untapped potential.

[marknutter]

It doesn't need to be spammy. If it were me, I would just feel a little more incentive to post about it on Twitter/FB and other places than I would otherwise. Brilliant idea.