It is as if the restaurant is paying for a good review that will not specifically be labeled an advertisement.
Of course, it could be argued that it is the critic's responsibility to conceal his or her identity, and the restaurant can do what it likes to receive a good review as part of its on-site advertising campaign. But while providing good service -- like giving a customer on a 'tipping' chair a new seat, or making sure the bread is fresh -- might not cross the ethical line, free food or service above and beyond what the average diner could hope to obtain seems to be a false form of promotion for the establishment.
The solution is to provide good service to every customer, regardless of the patron's identity. The legendary owner of a successful chain of restaurants, Danny Myer, who operates the Union Square Cafe, is famous for treating every customer like a king or queen for the night, including offering complementary umbrellas to diners who must leave during an unexpected shower. (of course, the umbrellas have the name of the restaurant prominently displayed upon them!)
If a restaurant must try that hard to change its approach for a reviewer, there is something wrong with the restaurant on a deeper level than a simple 'bad night' for which it must compensate. Putting a reviewer in the uncomfortable place of having to refuse a free dinner and free food might actually prejudice an ethical reviewer against the restaurant. Finally, quite often it is word-of-mouth rather than the printed word, especially for neighborhood establishments that draws the restaurant's core clientele. A truly good restaurant is critic-proof if it provides exceptional service.
Reference
Colapinto, John. (2009, November 16) Why restaurant critics need anonymity. The New Yorker
Retrieved March 22, 2010
http://www.newyorker.com/online/blogs/newsdesk/2009/11/john-colapinto-restaurant-critics-anonymity.html#ixzz0iwSsbB8g
