So whats in it for the other person??

LOL.

Sky have been doing referrals for years. On Money Saving Expert, members pay people for their referral. So, for example, if you allow me to refer you, we both get £50 vouchers and I pay you £25 by Paypal for the 'free referral'. That way, the person who joined Sky gets half of the referral that was never meant to be there anyway.