Mark Kleiman points out that a Los Angeles County regulation requiring restaurants to post the results of their health inspections appears to have reduced hospital admissions for food-related illnesses by 20 percent. Kleiman challenges libertarians to argue against this type of government regulation, given its obvious positive effects on the county's diners. I would go even further: health codes for restaurants benefit (acceptably hygienic) restaurants themselves, as well as their patrons. With the regulations in place, customers feel safer eating at a restaurant, and especially trying out a new one, and are thus more likely to dine out in general.
Of course, diehard libertarians will argue that private inspection services could substitute for the public authority, enforcing sanitary practices by contract. But that would require restaurant patrons to take the trouble not only to examine each restaurant's private certification, but also to investigate the reliability of various inspection services and the authenticity of the restaurant's claim to have been certified by them.
More generally, the entire libertarian obsession with private contractual alternatives to government regulation is massively inconsistent. In fact, the enforcement of real-world contracts often relies on a rich, complex web of governmentally-determined laws, rules, conventions and institutions that make health department regulations look positively anarchistic by comparison. For example, private restaurant inspection services would inevitably depend on the conventions governing trademark protection and the "implicit contracts" that restaurants are said to make with their customers merely by, say, posting an inspection service logo.
Now, this array of legal constructions is quite defensible on pragmatic grounds. But then, government health regulations are also defensible--indeed, clearly preferable--on pragmatic grounds. (After all, government health regulations don't preclude private inspection services, if the latter happen to offer any practical advantages.) Libertarians therefore tend to justify relying on private solutions by invoking fundamental principles like "non-coercion" and "private, voluntary contract"--principles that they are then happy to fudge when necessary to create feasible contractual solutions to problems like policing restaurant hygiene.