Dear Rich: The book we are writing contains MLB players' names and positions to illustrate a metaphor comparing an investment portfolio to a baseball team. It could be written without the names, but they add value, which is where the question might come in.
I read at the Stanford Library Fair Use site that nonfiction books fall under "informational use" rather than "commercial use." The cases on that site make me feel the law's interpreted based on the weather that day. And through this link on your blog I read that mentioning company names in fictional accounts is not a problem.
We won't use player names or MLB-trademark terms (which is about everything BUT the word baseball) to advertise. We think that your use of MLB player names and positions as a metaphor for investment is an informational use, and is likely to be protected under the first amendment. The distinction between informational and commercial uses is not a bright line, but when making the determination, you should focus on how the celebrity or trademark is used within the content ... not whether the content itself is sold. For example, newspapers and books may be sold to consumers but they may contain informational uses of celebrities and trademarks. On the other hand, giving away a celebrity t-shirt in return for a donation to a nonprofit may be considered as a commercial use. It often comes down to whether the celebrity is being directly exploited to endorse something. (FYI Dept. Much of the stuff written at the Stanford Fair Use site was written by the Dear Rich staff and is from our book, Getting Permission ... just sayin')