|Lee Moyer: Diet Coke Dragon|
I write second-world high fantasy. There shouldn't be any specific references to any modern-day, USA, earth-eccentric anythings mentioned. That's 80% of the joy of writing in that sub-genre.
I mean, I do use animals indigenous to earth. Animals that exist today but may be extinct by end of the decade. I may even be so bold as to use animals that went extinct within the last 100 years, but whose form or name are familiar with a modern audience.
Then again, I also use animals that are utterly made-up. In my current WiP I'm creating monsters and mashing together cross-breed weres.
Now, if I were to write contemporary fantasy, would I use contemporary references in my work? Places, yes. Readers get a kick out of that. Brand names, no. Why? See below. Celebrities, only if they're dead and can't do more damage to their reputation (I'm lookin' at you, Bill Cosby). Song lyrics -- hell no. That's creative and copyright infringement. Naming works of art, sure, but I'd try to stick to the stuff in museums. That way, if the reader didn't know to what I was referring, they could look it up.
Three reasons for the No Brands rule:
1) You shine favorable light on a brand that ends up doing pretty despicable things post-publication. Now you and your book are forever associated with Evil Brand.
2) Your book becomes a national phenomenon. You've mentioned certain brands. Perhaps your characters convert the framing room of a Hobby Lobby into a abortion clinic. Hobby Lobby is run by a deeply religious and litigious group of people. They sue you for libel and possibly trademark infringement.
3) I forget which famous author said this but the gist is "I'm not being paid to market their brand. If they want to pay me for product placement, then, by god, every character will be wearing Nike shoes and Calvin Klein shirts while drinking Coke."
Clearly, I choose the easiest path to avoid dating my work by writing stories that leverage only contemporary concepts.