Quoting from link below:
GrubHub / Seamless owns MenuPages, Allmenus, Restaurants on the Run, DiningIn, and Delivered Dish.
Seamless takes a percentage, not a flat fee, of the total food and beverage amount, even though its involvement is the same whether an order is for $10 or $250. Restaurants can choose from four commission levels (12.5%, 15%, 17.5%, and 20%); the more a restaurant pays, the higher up it will appear in the search results. When you search for restaurants on Seamless, you may have noticed that, in the default view, the results appear to be random, but they’re actually arranged by who paid what.
And unlike with, say, Google search results, there’s no disclaimer.
http://tribecacitizen.com/2016/03/01/why-restaurants-hate-gr...