According to the official AdSense blog, significant changes are coming to AdSense referrals. First, it's important to note that these changes only apply to referral ads for promoting AdSense; referrals for other products will not be affected. Future changes will vary depending on the user's geographic location.
Pricing changes for users in North America, Latin America, and Japan
Previously, the AdSense referral reward program was: "If a publisher referred by you registers for Google AdSense and within 180...