Attention to detail is important in all endeavors, including content writing. While blatantly making up facts, figures or sources is an obvious no-no, a content writer should also be cognizant that not every source is as credible as the next. Looking over writing samples, are there links to credible sources (medical journals, direct quotes from experts, respected newspapers like the Wall Street Journal or New York Times, etc.), or are the links from user-contributed sites like Wikipedia where there is little to no oversight? Keep in mind that every word on your site is a reflection of you and your business, whether you wrote it or not.