By referring friends, neighbors, or others to the site, you earn points! Referrals can be acquired by visiting either the Link-to-Us page or by copying and pasting the link given in your profile settings. Referral points are only rewarded after the user clicks the link and signs up for an account. Any abuse found in creating multiple accounts to earn points will result in a ban from the website.
This is from the FAQ/Help site here:
Please please *please* read the help on the site before posting questions like this..
I've been talking to some of the moderators. After the recent activity with phony referrals, the mods are thinking about taking them away, so users no longer get AP from referrals. Personally, I agree with this. If you think AG is cool you should share it with your friends. There shouldn't be an AP incentive.