How do sites know bussinesses are legit?

So this is kind of a weird question, but I've been wondering this for a while...
How do sites like citysearch or chowhound know if a business is actually who they say they are? How do they verify that whoever is making the post/providing info is indeed an employee of each respective business? Do they call? Do they check against some sort of food or liqour liscence database?Do they just say whatever and let the user do what they want?
 
 

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