If your topic is very specific, like Oprah, I wouldn't pay any mind to what other guides have up. You're supposed to be the expert, so feel free to assert that right. My approach is to write the articles my site needs (the core articles) and not worry about what anyone else has written until afterwards. That way, I don't have to worry about inadvertently taking their ideas and I don't have to worry about how I "spin" it. I have a broad topic, so I link to articles from guides who have more expertise than I do. For example, I might write an article about what features to look for in a family printer, but link to the printer guide's list of best family printers.
There are a number of guides who have content that is most appropriate for my site, even though it makes sense for theirs. Like the parenting K-6 guide has an article on the Family Computer (which, to my chagrin, ranks higher than anything on my site for those keywords...). Although it makes sense for her site, it makes more sense for mine, so I wouldn't think twice about putting up a similar article if I needed it. That's why they hired me. =}
Remember that you are paid for PVs, so it doesn't benefit you to link to other articles when you can write your own. The type of articles you may want to link to are things like "How to get tickets to your favorite day time talk show" or "Education for Girls in South Africa" (I don't know if there are articles like that!) or things that are relevant to the topic, but more the focus of another guide.
Two cents!
Christy