A trend I’ve noticed, not only in a book I reviewed recently but in other situations, is the profligate use of trademark symbols (® and ™). Unless you’re the trademark holder yourself, there is no real need to use them: just capitalize trade or brand names if you’re referring to them specifically, or use the generic equivalent if you’re not.
Here is what the Chicago Manual of Style has to say about this:
Brand names that are registered trademarks — often so indicated in dictionaries — should be capitalized if they must be used. A better choice is to substitute a generic term when available. Although the symbols ® and ™ often accompany trademark names on product packaging and in promotional material, there is no legal requirement to use these symbols, and they should be omitted wherever possible. Note also that some companies want people to use both the proper and the generic terms in reference to their products (“Kleenex facial tissue,” not just “Kleenex”), but here again there is no legal requirement. (Chicago Manual of Style, 15th edition, 8.162, p. 365)
I think that writers feel they must put the symbols in because the trademark holders do so, especially if, as was the case with one of the authors of Arthritis Without Pain, they have an ongoing relationship with the company holding the trademark. But the trademark holders insert them because they have to, to assert their trademark rights; you don’t, because it’s not your trademark.
It’s important to remember why the trademark symbol is there. It’s not part of the name itself, but a trademark notice: ® says that something is a registered trademark, ™ that it’s being claimed as one. The symbols are, in other words, a shorthand way of saying that a name is off-limits. (“Starship Enterprise™” basically means “You can write a TV series about a starship, but you’ll hear from our lawyers if you call your ship the Enterprise.”)
To understand where trademark holders are come from, remember that trademarks stop being trademarks when they become “generic through common use” — i.e., when people stop associating the trademark with the specific company that once owned it. For example, “Aspirin” is no longer a trademark for acetylsalicylic acid in the United States (though it’s still a trademark in Canada) because, I suppose, it was held that people no longer associated the name with Bayer, the trademark holder. Because of this, trademark holders get squirrelly when their trademarks are used as nouns or verbs rather than adjectives, i.e., “Google” for searching, “Xerox” for photocopying, “Photoshop” for image manipulation. Especially if they’re used as verbs with their competitors’ products.
So, while you don’t have to use the trademark symbols yourself, as a matter of writing style, you also shouldn’t use trademarked names if the generic version will suffice for your purposes. For example, you could use “Tylenol” only if you were writing something specifically about Johnson & Johnson’s brand of acetominophen (paracetamol), rather than the drug itself; otherwise, use the generic name.
See also the International Trademark Association’s publishing FAQ which says, among other things, that permission is generally not required to use a trademark in a fashion that is merely descriptive, and that trademark owners only need to use the ® or ™ symbol once in a document. (As Dan Santow points out, on the use of trademark symbols every single time the trademark appears, “when it comes to readability, trademark-o-mania makes copy appear choppy, difficult to read, and inelegant to the ear.”)