Zagat (pronounced “Za-GAT”) began in 1979 by Tim and Nina Zagat as a survey to rate restaurants in New York City; Zagat.com and Zagat guides now rate other business fields, such as hotels, music and movies. Someone who uses Zagat or who contributes to a Zagat survey is called a “Zagateer.” The term “Zagateer” has been cited in print since at least the early 1990s (1991 and 1995).
 
A similar term for an amateur who reviews restaurants is “Yelper” (for Yelp.com).
   
 
Wikipedia: Zagat
Zagat Survey /zəˈɡæt/ was established by Tim and Nina Zagat in 1979 as a way to collect and correlate the ratings of restaurants by diners. For their first guide, covering New York City, the Zagats surveyed their friends. As of 2005, the Zagat Survey included 70 cities, with reviews based on the input of 250,000 individuals reporting over the years. In addition to restaurants, Zagat guides rate hotels, nightlife, shopping, zoos, music, movies, theaters, golf courses, and airlines. The guides are sold in book form, and formerly as a paid subscription on its web site.
 
As of May 2012, as part of its acquisition by Google in September 2011, Zagat reviews and ratings became tightly integrated into Google’s services, and the Zagat.com site became free to use.
 
13 December 1991, St. Petersburg (FL) Times, “New in the ‘Hood” by Chris Sherman, Weekend, pg. 40:
And the first Zagateer of Orlando and Central Florida (including us) is due out at year’s end.
     
Google Books
Bottom Line Business
Volume 24, Issues 11-24
1995
Pg. 24:
Anyone can become a Zagateer, as they are sometimes called, by simply writing in and sending a stamped, self-addressed, business-sized envelope.
   
Google Books
Hawaii Magazine
Volumes 12-13
1995
Pg. 560:
The Zagateers were self-selecting noshers of infinite patience who filled out long, detailed questionnaires to rank each restaurant, according to Tim Zagat, publisher with his wife, Nina, of the successful restaurant guide.
 
25 May 2001, Rocky Mountain News (Denver, CO), “May the all-mightiest BBQ win” by John Lehndorff:
BE A ZAGATEER: Now’s the time for all good Colorado food lovers to share the knowledge they’ve gained by eating at all those restaurants this year.
 
New York (NY) Times
Eat and Tell
By DONALD G. McNEIL Jr.
Published: November 4, 2008
YOU too can be a restaurant critic. And not just an anonymous Zagateer, dutifully filling in forms.
(...)
It’s simple. Just sign up at Yelp.com and review away.
   
Time magazine
Zag-At the Movies: ‘Real People’ Pick Their ‘Best Films’
By Richard Corliss Wednesday, Oct. 20, 2010
(...)
The Zagateers are a bit less anachronistic in their choices of all-time favorite actors (Cary Grant, the leader, is followed by George Clooney and Johnny Depp) and actresses (Meryl Streep, then Sandra Bullock and Katharine Hepburn).
 
Google Books
Comfort Me with Offal:
Ruth Bourdain’s Guide to Gastronomy
By Ruth Bourdain (Josh Friedland)
Kansas City, MO: Andrews McMeel Publishing
2012
Pg. ?:
Zagateers: Somewhat “staid,” this group of restaurant-goers “won’t go anywhere” without their “little red books,” the Zagat Survey restaurant guides. ZAGATEERS tend to skew older and find new food media such as Yelp and food blogs to be a “mystery.”