Day 27 of 30 - social media

I'm thinking of offering free membership to the first 10 people to apply and refer 10 others who then apply... what do you think?  Would you apply if I posted that to Facebook or Twitter or would you be more likely to pay for membership if a friend encouraged you to pay to become a member?  I'm honestly interested in your answers... it would just be a single Facebook message or Tweet from me so I wouldn't constantly be advertising it every hour of every day and it would only be the first 10 people to apply that would be free - is that enough though?