Frank Ettin said:
It can be very much a "chicken-or-egg" matter: one reason that trademark litigation can be so complex and expensive; and a reason that owners of trademark who want to protect them are so aggressive about litigating infringements.
^^^ This.
Ever sit down in a restaurant that serves Pepsi products and ask for a "Diet Coke"? At least in this corner of the universe, the waitperson is always VERY careful to say, "We don't have Coca Cola here, is a Diet Pepsi okay?"
And generally it is okay. Who cares, cola is cola, right? But I asked once, MANY years ago, why a waitress was so careful to point out that I'd be getting a Diet Pepsi rather than a Diet Coke. She explained that Coca Cola has mystery shoppers who do nothing other than seek out restaurants who serve Pepsi products and
don't make that clear if a customer orders a "Coke."
That was many years ago, and I don't know if the explanation was true even then but it made sense. And I noticed just yesterday that a waitress carefully pointed out when my wife asked for a Diet Coke that "We don't have Diet Coke, is Diet Pepsi okay?" Coca Cola has to do that, otherwise "Coke" will become a generic description, just as happened with Kleenex and Xerox.