Restaurant report cards caught my eye on my very first visit to Los Angeles. Displayed prominently in or near the entrance to every eatery, the blue A, green B or red C quickly communicate what a presumably impartial, knowledgeable observer recently thought of the restaurant's cleanliness and food safety practices. The score cards are required by law in almost every city in Los Angeles County. Los Angeles County allows the health-conscious and the curious can search out restaurants by name, geographic location and/or inspection score online.
San Francisco City and County amended its health code in 2004 to create its own take on restaurant report cards: any eatery scoring 90% or higher in its most recent food inspection report must post a Symbol of Excellence that is visible to customers. San Francisco has a cumbersome, search-by-name interface that reveals the most recent score of any restaurant.
The Los Angeles system works as both a carrot and a stick -- if consumers without strong brand loyalty are likely to choose an A-rated system over a B-rated establishment, all else being equal, then A-rated restaurants get more customers and B-rated customers get incentive to clean up their act. the San Francisco system is simply a gold star, joining the Zagat guide stickers and "Best of San Francisco" plaques as another inoffensive way of quietly distinguishing restaurants.
Why not require that every restaurant post its score? Perhaps the concern is motivated by a textbook privacy concern: the desire not to present potentially damning data about possibly subpar restaurants out of context.