copy from the shoppers website:
If you and at least one of your friends register online and then each spend $20 or more* on almost anything in-store, you’ll each receive 5,000 Shoppers Optimum Bonus Points® for your purchases.
You will also receive an additional 5,000 Shoppers Optimum Bonus Points for your friend’s purchase.
That’s 10,000 points!
PLUS you’ll receive another 5,000 Shoppers Optimum Bonus Points for every other friend that does the same up to a maximum of 55,000 points.