When I began my working career, I worked in the creative department in a small branch of one of the top advertising companies. Among things I had to be aware of are many copyright issues, like Kitty Litter is a brand name and not generic. Some brands are very protective. Disney as already mentioned! Band-aid for example is another trademarked name that does not wish to become generic. There is a small car dealership near me that I'm sure the Simpsons would not approve of their billboard, but no print or tv ads and so I don't turn them in.
And I used to be sent out as an undercover shopper to go to fast food chains that sell Pepsi products and ask for a Coke... they are supposed to correct you. If they didn't, we would report the incident and the more serious secret shoppers would be sent in until the lawyers sent corporate cease and desist letters.