Marketing guru Michael Stone at http://www.markupandprofit.com makes this (to me) surprising statement in his latest newsletter.
Let's be clear. The lack of leads so many are experiencing is due to working by referral only. Referrals should not make up more than 20 - 25 percent of all your business. If referrals are over 25 percent of your business, when the economy hits a little bump in the road you will see a drastic decline in calls into your company and sales. Advertise and stay with it. Let referrals be the icing on the cake.
You can subscribe to his newsletter by completing the form at his website. You may also want to read his Markup and Profit blog.