Virtually unknown 10 years ago, in 2005 there were 500 doctors practicing what's referred to as concierge medicine. Now there are 5,000, according to the Society for Innovative Medical Practice Design, a professional society of concierge physicians.

As with any business deal where you're being asked to pay hard, cold cash for an intangible service, the buyer should beware. "Just because they charge a fee and behave exclusively does not make them good," warns bioethicist Art Caplan.