We've all heard about the success of the Dropbox share-with-your-friends feature. Both parties benefit and everyone's happy. How can you incentivize referrals?

Think about what users want the most of. What allows them to defer payment by just a little bit (but not too much!). Build a system to share this deal with friends, either by email or posting to social networks. For a boost in conversions, put a time limit on the offer.

35% of Dropbox's new growth comes from multi-beneficial referrals: According to Drew Houston of Dropbox, 20% of their user growth comes from shared folders alone. Source: //brinx.it/fpz