Interesting. Does the person need you sign up through you, or just use your referral code at checkout? If it's the later, I wonder if you could target your keywords to "fab promo code" or "fab discount" to try to get people that were near the end of the purchase cycle and were just looking for a promo to complete their purchase.
Actually, it was simpler than that. The link on my ad went to a Fab.com sign up page that already had my referral code embedded. The user simply needed to make a purchase within the first 30 days to enable me to receive my referral credit. Many of the users I paid for most likely did buy something but not within the 30 day timeframe.
