Using a little bit of game theory in your business or process can really help.  People like to be things that they normally can't.  Give someone a clear easy, slightly fun way to earn 10 badges and they will do it.  

Another company that has used this to great success is foursquare.  

They have used the game edge to become quite successful in the more and more crowded field of location aware social networks.  

Also I really like how Listia makes it super simple to share a pre-supplied affiliate link.  When you ask someone to share you product or idea with their friends, you are asking a lot.  Make it as simple as possible.