My recent realisation has been these shops fall in a category of what I call "rating agency" all of which share common characteristics. For example; Moody's, Gartner, Michelin Stars.

1. Stripped of all the paraphernalia these are yellow pages ranked by popularity in their domains.

2. They are in the business of selling customers to the said businesses. So their primary customers are businesses; restaurants, mutual funds etc.,

3. They need to maintain authenticity of impartiality so it's not easy to find out how they make money.

4. Their secondary audience is decision makers; CIOs, money managers etc., Think of -- "no one got fired for picking at the 1st ranked software from Gartner's list", "But Moody's rated it AAA, how was I supposed to know that fund would tank". It's a terrific CYA tool.

5. I'd say about 80% of the times they do a decent job of stack ranking. But there is an element of virtuous cycle there. The top rated "things" are popular because they are ranked to be so by these rating companies. Once a critical mass adopts then that tech/restaurant/etc indeed becomes numerically popular.