Referrals have just lost their charm now. People refer anybody and everybody. This happens even more in cases where a company gives a bonus for a successful referral.
Ideally, there should be some rating given to the referrers based on the quality of people they refer and how many of them make it through the interviews. That rating should remain private and based on it, companies should prioritize the referred candidates. Also, for a high failure rate, the referrer shouldn't be allowed to refer more candidates.